Method and device for efficient feedback in wireless communication system supporting multiple antennas

ABSTRACT

The present description relates to a wireless communication system, and more particularly, discloses a method and a device for efficient feedback in a wireless communication system supporting multiple antennas. According to one embodiment of the present invention, the method for transmitting channel status information on a downlink transmission through an uplink, in the wireless communication system, comprises the following steps: transmitting a rank indicator (RI) in a first subframe; transmitting a first precoding matrix index (PMI) in a second subframe; and transmitting a second PMI and channel quality information (CQI) in a third subframe, wherein the precoding matrix to be applied to the transmission of the downlink can be determined by a combination of the first and second PMIs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/641,058, filed on Oct. 12, 2012, currently pending, which is theNational Stage filing under 35 U.S.C. 371 of International ApplicationNo. PCT/KR2011/002572, filed on Apr. 12, 2011, which claims the benefitof U.S. Provisional Application Ser. No. 61/323,345, filed on Apr. 12,2010, and 61/334,948, filed on May 14, 2010, the contents of which areall hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present description relates to wireless communication system, andmore specifically, to a method and device for efficient feedback in awireless communication system supporting multiple antennas.

BACKGROUND ART

Multiple Input Multiple Output (MIMO) can increase the efficiency ofdata transmission and reception using multiple transmit antennas andmultiple receive antennas. According to MIMO, a transmitting end or areceiving end of a wireless communication system uses multiple antennasto improve communication capacity or performance. MIMO can also becalled a multi-antenna technology. For successful multi-antennatransmission, it is necessary to feedback information on a multi-antennachannel from a receiving end that receives the multi-antenna channel.

In a conventional multi-antenna wireless communication system, a rankindicator (RI), a precoding matrix index (PMI), channel qualityindicator (CQI), etc. are defined as information fed back to atransmitting end from a receiving end. This feedback information isconfigured as information suitable for conventional multi-antennatransmission.

Introduction of a new system having an extended antenna configurationcompared to the conventional multi-antenna wireless communication systemis under discussion. For example, a new system having an extendedantenna configuration can provide improved system capacity by supportingMIMO transmission through 8 transmit antennas, whereas the conventionsystem supports up to 4 transmit antennas.

DISCLOSURE Technical Problem

The new system supporting an extended antenna configuration performsmore complicated MIMO transmission than conventional MIMO transmission,and thus it is impossible to support MIMO transmission operation of thenew system using only feedback information defined for the conventionalMIMO transmission.

An object of the present invention is to provide a method and device forconfiguring and transmitting feedback information for properly andefficiently supporting MIMO transmission according to an extendedantenna configuration.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solution

According to one aspect of the present invention, a method fortransmitting channel state information on downlink transmission throughan uplink in a wireless communication system includes: transmitting arank indicator (RI) in a first subframe; transmitting a first precodingmatrix indicator (PMI) in a second subframe; and transmitting a secondPMI and a channel quality indicator (CQI) in a third subframe, wherein apreferred precoding matrix of a UE is indicated by a combination of thefirst PMI and the second PMI.

According to another aspect of the present invention, a method forreceiving channel state information on downlink transmission through anuplink in a wireless communication system includes: receiving an RI in afirst subframe; receiving a first PMI in a second subframe; andreceiving a second PMI and a CQI in a third subframe, wherein apreferred precoding matrix of a UE is indicated by a combination of thefirst PMI and the second PMI.

According to another aspect of the present invention, a user equipment(UE) transmitting channel state information on downlink transmissionthrough an uplink in a wireless communication system includes: areception module for receiving a downlink signal from an eNB; atransmission module for transmitting an uplink signal to the eNB; and aprocessor for controlling the UE including the reception module and thetransmission module, wherein the processor transmits an RI in a firstsubframe, transmits a first PMI in a second subframe and transmits asecond PMI and a CQI in a third subframe, through the transmissionmodule, wherein a preferred precoding matrix of a UE is indicated by acombination of the first PMI and the second PMI.

According to another aspect of the present invention, an eNB receivingchannel state information on downlink transmission through an uplink ina wireless communication system includes: a reception module forreceiving an uplink signal from a UE; a transmission module fortransmitting a downlink signal to the UE; and a processor forcontrolling the eNB including the reception module and the transmissionmodule, wherein the processor receives an RI in a first subframe,receives a first PMI in a second subframe and receives a second PMI anda CQI in a third subframe, through the reception module, wherein apreferred precoding matrix of a UE is indicated by a combination of thefirst PMI and the second PMI.

The following can be commonly applied to the above embodiments of thepresent invention.

The first PMI may indicate precoding matrix candidates applied to thedownlink transmission and the second PMI may indicate one of theprecoding matrix candidates.

The RI may be transmitted on a physical uplink control channel (PUCCH)of the first subframe, the first PMI may be transmitted on a PUCCH ofthe second subframe, and the second PMI and the CQI may be transmittedon a PUCCH of the third subframe.

The RI, the first PMI, the second PMI and the CQI may correspond tochannel state information about downlink 8-transmit antennatransmission.

The RI, the first PMI, the second PMI and the CQI may correspond tofeedback information about a wideband.

The RI may be transmitted according to a first reporting period, thefirst PMI may be transmitted according to a second reporting period, andthe second PMI and the CQI may be transmitted according to a thirdreporting period.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Advantageous Effects

According to embodiment of the present invention, it is possible toprovide a method and device for configuring and transmitting feedbackinformation for properly and efficiently supporting MIMO transmissionaccording to an extended antenna configuration.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIGS. 1A and 1B illustrate an exemplary radio frame structure;

FIG. 2 illustrates a resource grid in a downlink slot;

FIG. 3 illustrates a downlink subframe structure;

FIG. 4 illustrates an uplink subframe structure;

FIGS. 5A and 5B illustrate a physical layer (L1) and a MAC layer (L2))of a multicarrier supporting system;

FIG. 6 is a conceptual diagram for illustrating component carriers (CCs)for downlink and uplink;

FIG. 7 illustrates an example of DL/UL CC connection;

FIG. 8 illustrates SC-FDMA and OFDMA transmission schemes;

FIGS. 9A to 9C illustrate maximum transmit power in the case of singleantenna transmission and multi-antenna transmission;

FIGS. 10A and 10B show a configuration of a MIMO communication system;

FIGS. 11A and 11B show a normal CCD structure in a MIMO system;

FIG. 12 is a diagram for illustrating codebook based precoding;

FIG. 13 illustrates a resource mapping structure of a PUCCH;

FIGS. 14A and 14B illustrate channel structures of CQI bits;

FIG. 15 is a diagram for illustrating transmission of CQI and ACK/NACKinformation;

FIG. 16 is a diagram for illustrating feedback of channel stateinformation;

FIG. 17 is a diagram for illustrating an exemplary CQI reporting mode;

FIG. 18 illustrates an exemplary periodic channel informationtransmission scheme of user equipment (UE);

FIG. 19 is a diagram for illustrating transmission of an SB CQI;

FIG. 20 is a diagram for illustrating a WB CQI and an SB CQI;

FIG. 21 is a diagram for illustrating a WB CQI, an SB CQI and an RI;

FIGS. 22 and 23 is a diagram for illustrating channel state informationreporting periods;

FIG. 24 is a flowchart illustrating a channel state informationtransmission method according to an embodiment of the present invention;and

FIG. 25 shows configurations of a base station (BS) and a UE accordingto an embodiment of the present invention.

BEST MODE

Embodiments described hereinbelow are combinations of elements andfeatures of the present invention. The elements or features may beconsidered selective unless otherwise mentioned. Each element or featuremay be practiced without being combined with other elements or features.Further, an embodiment of the present invention may be constructed bycombining parts of the elements and/or features. Operation ordersdescribed in embodiments of the present invention may be rearranged.Some constructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between abase station (BS) and a User Equipment (UE). The BS is a terminal nodeof a network, which communicates directly with a UE. In some cases, aspecific operation described as performed by the BS may be performed byan upper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘evolved Node B (eNode B or eNB)’, ‘Access Point(AP)’, etc. The term ‘UE’ may be replaced with the term ‘terminal’,‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’, ‘SubscriberStation (SS)’, etc.

Specific terms used for the embodiments of the present invention areprovided to help the understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention can be supported by standarddocuments disclosed for at least one of wireless access systems,Institute of Electrical and Electronics Engineers (IEEE) 802, 3^(rd)Generation Partnership Project (3GPP), 3GPP Long Term Evolution (3GPPLTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are notdescribed to clarify the technical features of the present invention canbe supported by those documents. Further, all terms as set forth hereincan be explained by the standard documents.

Techniques described herein can be used in various wireless accesssystems such as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier-FrequencyDivision Multiple Access (SC-FDMA), etc. CDMA may be implemented as aradio technology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may beimplemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a partof Universal Mobile Telecommunication System (UMTS). 3GPP LTE is a partof Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA fordownlink and SC-FDMA for uplink. LTE-A is an evolution of 3GPP LTE.WiMAX can be described by the IEEE 802.16e standard (WirelessMetropolitan Area Network (WirelessMAN-OFDMA Reference System) and theIEEE 802.16m standard (WirelessMAN-OFDMA Advanced System). For clarity,this application focuses on the 3GPP LTE/LTE-A system. However, thetechnical features of the present invention are not limited thereto.

A downlink radio frame structure will now be described with reference toFIGS. 1A and 1B.

In a cellular OFDM radio packet communication system, uplink/downlinkdata packet transmission is performed subframe by subframe. A subframeis defined as a predetermined time interval including a plurality ofOFDM symbols. 3GPP LTE standard supports type 1 radio frame structureapplicable to frequency division duplex (FDD) and type 2 radio framestructure applicable to time division duplex (TDD).

FIG. 1A shows the type 1 radio frame structure. A downlink radio frameis divided into 10 subframes. Each subframe is further divided into twoslots in the time domain. A unit time during which one subframe istransmitted is defined as Transmission Time Interval (TTI). For example,one subframe may be 1 ms in duration and one slot may be 0.5 ms induration. A slot may include a plurality of OFDM symbols in the timedomain and include a plurality of resource blocks (RBs) in the frequencydomain. Because the 3GPP LTE system adopts OFDMA for downlink, an OFDMsymbol represents one symbol period. An OFDM symbol may be referred toas an SC-FDMA symbol or symbol period. A Resource Block (RB) is aresource allocation unit including a plurality of contiguous subcarriersin a slot.

The number of OFDM symbols included in one slot may be changed accordingto the configuration of a Cyclic Prefix (CP). There are an extended CPand a normal CP. For example, the number of OFDM symbols included in oneslot may be seven in case of a normal CP. In case of an extended CP, thelength of one OFDM symbol is increased and thus the number of OFDMsymbols included in one slot is less than that in case of a normal CP.In case of the extended CP, for example, the number of OFDM symbolsincluded in one slot may be six. If a channel state is instable as isthe case when a UE moves fast, the extended CP may be used in order tofurther reduce inter-symbol interference.

In case of a normal CP, since one slot includes seven OFDM symbols, onesubframe includes 14 OFDM symbols. The first two or three OFDM symbolsof each subframe may be allocated to a Physical Downlink Control Channel(PDCCH) and the remaining OFDM symbols may be allocated to a PhysicalDownlink Shared Channel (PDSCH).

The structure of a type 2 radio frame is shown in FIG. 1B. The type 2radio frame includes two half-frames, each of which is made up of fivesubframes, a downlink pilot time slot (DwPTS), a guard period (GP), andan uplink pilot time slot (UpPTS), in which one subframe consists of twoslots. DwPTS is used to perform initial cell search, synchronization, orchannel estimation. UpPTS is used to perform channel estimation of abase station and uplink transmission synchronization of a UE. The guardinterval (GP) is located between an uplink and a downlink so as toremove interference generated in the uplink due to multi-path delay of adownlink signal. One subframe is composed of two slots irrespective ofthe radio frame type.

The structure of the radio frame is only exemplary. Accordingly, thenumber of subframes included in the radio frame, the number of slotsincluded in the subframe or the number of symbols included in the slotmay be changed in various manners.

FIG. 2 is a diagram showing a resource grid in a downlink slot. Althoughone downlink slot includes seven OFDM symbols in the time domain and oneRB includes 12 subcarriers in the frequency domain in the figure, thescope or spirit of the present invention is not limited thereto. Forexample, in case of a normal Cyclic Prefix (CP), one slot includes 7OFDM symbols. However, in case of an extended CP, one slot may include 6OFDM symbols. Each element on the resource grid is referred to as aresource element. One RB includes 12×7 resource elements. The numberN^(DL) of RBs included in the downlink slot is determined based ondownlink transmission bandwidth. The structure of the uplink slot may beequal to the structure of the downlink slot.

FIG. 3 is a diagram showing the structure of a downlink subframe. Amaximum of three OFDM symbols of a front portion of a first slot withinone subframe corresponds to a control region to which a control channelis allocated. The remaining OFDM symbols correspond to a data region towhich a Physical Downlink Shared Channel (PDSCH) is allocated. Examplesof the downlink control channels used in the 3GPP LTE system include,for example, a Physical Control Format Indicator Channel (PCFICH), aPhysical Downlink Control Channel (PDCCH), a Physical Hybrid automaticrepeat request Indicator Channel (PHICH), etc. The PCFICH is transmittedat a first OFDM symbol of a subframe, and includes information about thenumber of OFDM symbols used to transmit the control channel in thesubframe. The PHICH includes a HARQ ACK/NACK signal as a response touplink transmission. The control information transmitted through thePDCCH is referred to as Downlink Control Information (DCI). The DCIincludes uplink or downlink scheduling information or an uplink transmitpower control command for a certain UE group. The PDCCH may includeresource allocation and transmission format of a Downlink Shared Channel(DL-SCH), resource allocation information of an Uplink Shared Channel(UL-SCH), paging information of a Paging Channel (PCH), systeminformation on the DL-SCH, resource allocation of a higher layer controlmessage such as a Random Access Response (RAR) transmitted on the PDSCH,a set of transmit power control commands for individual UEs in a certainUE group, transmit power control information, activation of Voice overIP (VoIP), etc. A plurality of PDCCHs may be transmitted within thecontrol region. The UE may monitor the plurality of PDCCHs. The PDCCHsare transmitted on an aggregation of one or several contiguous controlchannel elements (CCEs). The CCE is a logical allocation unit used toprovide the PDCCHs at a coding rate based on the state of a radiochannel. The CCE corresponds to a plurality of resource element groups.The format of the PDCCH and the number of available bits are determinedbased on a correlation between the number of CCEs and the coding rateprovided by the CCEs. The base station determines a PDCCH formataccording to a DCI to be transmitted to the UE, and attaches a CyclicRedundancy Check (CRC) to control information. The CRC is masked with aRadio Network Temporary Identifier (RNTI) according to an owner or usageof the PDCCH. If the PDCCH is for a specific UE, a cell-RNTI (C-RNTI) ofthe UE may be masked to the CRC. Alternatively, if the PDCCH is for apaging message, a paging indicator identifier (P-RNTI) may be masked tothe CRC. If the PDCCH is for system information (more specifically, asystem information block (SIB)), a system information identifier and asystem information RNTI (SI-RNTI) may be masked to the CRC. To indicatea random access response that is a response for transmission of a randomaccess preamble of the UE, a random access-RNTI (RA-RNTI) may be maskedto the CRC.

FIG. 4 is a diagram showing the structure of an uplink frame. The uplinksubframe may be divided into a control region and a data region in afrequency region. A Physical Uplink Control Channel (PUCCH) includinguplink control information is allocated to the control region. APhysical uplink Shared Channel (PUSCH) including user data is allocatedto the data region. In order to maintain single carrier characteristics,one UE does not simultaneously transmit the PUCCH and the PUSCH. ThePUCCH for one UE is allocated to an RB pair in a subframe. RBs belongingto the RB pair occupy different subcarriers with respect to two slots.Thus, the RB pair allocated to the PUCCH is “frequency-hopped” at a slotedge.

Carrier Aggregation

Although downlink and uplink bandwidths are different from each other, awireless communication system typically uses one carrier. For example, awireless communication system having one carrier for each of thedownlink and the uplink and symmetry between the downlink and uplinkbandwidths may be provided based on a single carrier.

The International Telecommunication Union (ITU) requests thatIMT-Advanced candidates support wider bandwidths, compared to legacywireless communication systems. However, allocation of a wide frequencybandwidth is difficult throughout most of the world. Accordingly, atechnology for efficiently using small segmented bands, known as carrieraggregation (bandwidth aggregation) or spectrum aggregation, has beendeveloped in order to aggregate a plurality of physical bands to a widerlogical band.

Carrier aggregation was introduced to support increased throughput,prevent cost increase caused by introduction of wideband RF devices, andensure compatibility with legacy systems. Carrier aggregation enablesdata exchange between a UE and a BS through a group of carriers eachhaving a bandwidth unit defined in a legacy wireless communicationsystem (e.g. 3GPP LTE Release-8 or Release-9 in case of 3GPP LTE-A). Thecarriers each having a bandwidth unit defined in the legacy wirelesscommunication system may be called Component Carriers (CCs). Carrieraggregation using one or more CCs may be applied to each of downlink anduplink. Carrier aggregation may support a system bandwidth of up to 100MHz by aggregating up to five CCs each having a bandwidth of 5, 10 or 20MHz.

A downlink CC and an uplink CC may be represented as a DL CC and a ULCC, respectively. A carrier or CC may be represented as a cell in termsof function in the 3GPP LTE system. Thus, a DL CC and a UL CC may bereferred to as a DL cell and a UL cell, respectively. Hereinbelow, theterms ‘carriers’, ‘component carriers’, ‘CCs’ or ‘cells’ will be used tosignify a plurality of carriers to which carrier aggregation is applied.

While the following description exemplarily uses a BS (or cell) as adownlink transmission entity and exemplarily uses a UE as an uplinktransmission entity, the scope or spirit of the present invention is notlimited thereto. That is, even when a relay node (RN) may be used as adownlink transmission entity from a BS to a UE and or be used as anuplink reception entity from a UE to a BS, or even when the RN may beused an uplink transmission entity for a UE or be used as a downlinkreception entity from a BS, it should be noted that the embodiments ofthe present invention can be applied without difficulty.

Downlink carrier aggregation may be described as a BS supportingdownlink transmission to a UE in frequency resources (subcarriers orphysical resource blocks [PRBs]) of one or more carrier bands in timeresources (allocated in units of a subframe). Uplink carrier aggregationmay be described as a UE supporting uplink transmission to a BS infrequency resources (subcarriers or PRBs) of one or more carrier bandsin time resources (allocated in units of a subframe).

FIGS. 5A and 5B show a physical layer (first layer, L1) and a MAC layer(second layer, L2) of a multi-carrier supported system. Referring toFIGS. 5A and 5B, a BS of the legacy wireless communication systemsupporting a single carrier includes one physical layer (PHY) entitycapable of supporting one carrier, and one medium access control (MAC)entity for controlling one PHY entity may be provided to the BS. Forexample, baseband processing may be carried out in the PHY layer. Forexample, the L1/L2 scheduler operation including not only MAC PDU(Protocol Data Unit) creation of a transmitter but also MAC/RLCsub-layers may be carried out in the MAC layer. The MAC PDU packet blockof the MAC layer is converted into a transport block through a logicaltransport layer, such that the resultant transport block is mapped to aphysical layer input information block. In FIGS. 5A and 5B, the MAClayer is represented as the entire L2 layer, and may conceptually coverMAC/RLC/PDCP sub-layers. For convenience of description and betterunderstanding of the present invention, the above-mentioned applicationmay be used interchangeably in the MAC layer description of the presentinvention.

On the other hand, a multicarrier-supporting system may provide aplurality of MAC-PHY entities. In more detail, as can be seen from FIG.5A, the transmitter and receiver of the multicarrier-supporting systemmay be configured in such a manner that one MAC-PHY entity is mapped toeach of n component carriers (n CCs). An independent PHY layer and anindependent MAC layer are assigned to each CC, such that a PDSCH foreach CC may be created in the range from the MAC PDU to the PHY layer.

Alternatively, the multicarrier-supporting system may provide one commonMAC entity and a plurality of PHY entities. That is, as shown in FIG.5B, the multicarrier-supporting system may include the transmitter andthe receiver in such a manner that n PHY entities respectivelycorrespond to n CCs and one common MAC entity controlling the n PHYentities may be present in each of the transmitter and the receiver. Inthis case, a MAC PDU from one MAC layer may be branched into a pluralityof transport blocks corresponding to a plurality of CCs through atransport layer. Alternatively, when generating a MAC PDU in the MAClayer or when generating an RLC PDU in the RLC layer, the MAC PDU or RLCPDU may be branched into individual CCs. As a result, a PDSCH for eachCC may be generated in the PHY layer.

PDCCH for transmitting L1/L2 control signaling control informationgenerated from a packet scheduler of the MAC layer may be mapped tophysical resources for each CC, and then transmitted. In this case,PDCCH that includes control information (DL assignment or UL grant) fortransmitting PDSCH or PUSCH to a specific UE may be separately encodedat every CC carrying the corresponding PDSCH/PUSCH. The PDCCH may becalled a separate coded PDCCH. On the other hand, PDSCH/PUSCHtransmission control information of several CCs may be configured in onePDCCH such that the configured PDCCH may be transmitted. This PDCCH maybe called a joint coded PDCCH.

To support carrier aggregation, connection between a BS and a UE (or RN)needs to be established and preparation of connection setup between theBS and the UE is needed in such a manner that a control channel (PDCCHor PUCCH) and/or a shared channel (PDSCH or PUSCH) can be transmitted.In order to perform the above-mentioned connection or connection setupfor a specific UE or RN, measurement and/or reporting for each carrierare needed, and CCs serving as the measurement and/or reporting targetsmay be assigned. In other words, CC assignment means that CCs(indicating the number of CCs and indexes of CCs) used for DL/ULtransmission are established in consideration of not only capabilitiesof a specific UE (or RN) from among UL/DL CCs constructed in the BS butalso system environment.

In this case, when CC assignment is controlled in third layer (L3) RadioResource Management (RRM), UE-specific or RN-specific RRC signaling maybe used. Alternatively, cell-specific or cell cluster-specific RRCsignaling may be used. Provided that dynamic control such as a series ofCC activation/deactivation settings is needed for CC assignment, apredetermined PDCCH may be used for L1/L2 control signaling, or adedicated physical control channel for CC assignment control informationor an L2 MAC-message formatted PDSCH may be used. On the other hand, ifCC assignment is controlled by a packet scheduler, a predetermined PDCCHmay be used for L1/L2 control signaling, a physical control channeldedicated for CC assignment control information may be used, or a PDSCHconfigured in the form of an L2 MAC message may be used.

FIG. 6 is a conceptual diagram illustrating downlink (DL) and uplink(UL) component carriers (CCs). Referring to FIG. 6, DL and UL CCs may beassigned from a BS (cell) or RN. For example, the number of DL CCs maybe set to N and the number of UL CCs may be set to M.

Through the UE's initial access or initial deployment process, after RRCconnection is established on the basis of one certain CC for DL or UL(cell search) (for example, system information acquisition/reception,initial random access process, etc.), a unique carrier setup for each UEmay be provided from a dedicated signaling (UE-specific RRC signaling orUE-specific L1/L2 PDCCH signaling). For example, assuming that a carriersetup for UE is commonly achieved in units of a BS (cell orcell-cluster), the UE carrier setup may also be provided throughcell-specific RRC signaling or cell-specific UE-common L1/L2 PDCCHsignaling. In another example, carrier component information for use ina BS may be signaled to a UE through system information for RRCconnection setup, or may also be signaled to additional systeminformation or cell-specific RRC signaling upon completion of the RRCconnection setup.

While DL/UL CC setup has been described, centering on the relationshipbetween a BS and a UE, to which the present invention is not limited, anRN may also provide DL/UL CC setup to a UE contained in an RN region. Inaddition, in association with an RN contained in a BS region, the BS mayalso provide DL/UL CC setup of the corresponding RN to the RN of the BSregion. For clarity, while the following description will disclose DL/ULCC setup on the basis of the relationship between the BS and the UE, itshould be noted that the same content may also be applied to therelationship between the RN and the UE (i.e., access uplink anddownlink) or the relation between the BS and the RN (backhaul uplink ordownlink) without departing from the scope or spirit of the presentinvention.

When the above-mentioned DL/UL CCs are uniquely assigned to individualUEs, DL/UL CC linkage may be implicitly or explicitly configured througha certain signaling parameter definition.

FIG. 7 shows an exemplary linkage of DL/UL CCs. In more detail, when aBS configures two DL CCs (DL CC #a and DL CC #b) and two UL CCs (UL CC#i and UL CC #j), FIG. 7 shows a DL/UL CC linkage defined when two DLCCs (DL CC #a and DL CC #b) and one UL CC (UL CC #i) are assigned to acertain UE. In a DL/UL CC linkage setup shown in FIG. 7, a solid lineindicates a linkage setup between DL CC and UL CC that are basicallyconstructed by a BS, and this linkage setup between DL CC and UL CC maybe defined in “System Information Block (SIB) 2”. In the DL/UL CClinkage setup shown in FIG. 7, a dotted line indicates a linkage setupbetween DL CC and UL CC configured in a specific UE. The above-mentionedDL CC and UL CC linkage setup shown in FIG. 7 is disclosed only forillustrative purposes, and the scope or spirit of the present inventionis not limited thereto. That is, in accordance with various embodimentsof the present invention, the number of DL CCs or UL CCs configured by aBS may be set to an arbitrary number. Thus, the number of UE-specific DLCCs or the number of UE-specific UL CCs in the above-mentioned DL CCs orUL CCs may be set to an arbitrary number, and associated DL/UL CClinkage may be defined in a different way from that of FIG. 7.

Further, from among DL CCs and UL CCs configured or assigned, a primaryCC (PCC), or a primary cell (P-cell) or an anchor CC (also called ananchor cell) may be configured. For example, a DL PCC (or DL P-cell)aiming to transmit configuration/reconfiguration information on RRCconnection setup may be configured. In another example, UL CC fortransmitting PUCCH to be used when a certain UE transmits UCI that mustbe transmitted on uplink may be configured as UL PCC (or UL P-cell). Forconvenience of description, it is assumed that one DL PCC (P-cell) andone UL PCC (P-cell) are basically assigned to each UE. Alternatively, ifa large number of CCs is assigned to UE or if CCs can be assigned from aplurality of BSs, one or more DL PCCs (P-cells) and/or one or more ULPCCs (P-cells) may be assigned from one or more BSs to a certain UE. Forlinkage between DL PCC (P-cell) and UL PCC (P-cell), a UE-specificconfiguration method may be considered by the BS as necessary. Toimplement a more simplified method, a linkage between DL PCC (P-cell)and UL PCC (P-cell) may be configured on the basis of the relationshipof basic linkage that has been defined in LTE Release-8 (LTE Rel-8) andsignaled to System Information Block (or Base) 2. DL PCC (P-cell) and ULPCC (P-cell) for the above-mentioned linkage configuration are groupedso that the grouped result may be denoted by a UE-specific P-cell.

SC-FDMA Transmission and OFDMA Transmission

FIG. 8 is a conceptual diagram illustrating an SC-FDMA transmissionscheme and an OFDMA transmission scheme for use in a mobilecommunication system. The SC-FDMA transmission scheme may be used for ULtransmission and the OFDMA transmission scheme may be used for DLtransmission.

Each of the UL signal transmission entity (e.g., UE) and the DL signaltransmission entity (e.g., BS) may include a Serial-to-Parallel (S/P)Converter 801, a subcarrier mapper 803, an M-point Inverse DiscreteFourier Transform (IDFT) module 804, and a Parallel-to-Serial Converter805. Each input signal that is input to the S/P converter 801 may be achannel coded and modulated data symbol. However, a user equipment (UE)for transmitting signals according to the SC-FDMA scheme may furtherinclude an N-point Discrete Fourier Transform (DFT) module 802. Theinfluence of IDFT processing of the M-point IDFT module 804 isconsiderably offset, such that a transmission signal may be designed tohave a single carrier property. That is, the DFT module 802 performs DFTspreading of an input data symbol such that a single carrier propertyrequisite for UL transmission may be satisfied. The SC-FDMA transmissionscheme basically provides good or superior Peak to Average Power ratio(PAPR) or Cubic Metric (CM), such that the UL transmitter can moreeffectively transmit data or information even in the case of the powerlimitation situation, resulting in an increase in user throughput.

FIGS. 9A to 9C are conceptual diagrams illustrating maximum transmissionpower for single antenna transmission and MIMO transmission. FIG. 9Ashows the case of single antenna transmission. As can be seen from FIG.9A, one power amplifier (PA) may be provided to one antenna. In FIG. 9A,an output signal (P_(max)) of the power amplifier (PA) may have aspecific value, for example, 23 dBm. In contrast, FIGS. 9B and 9C showthe case of MIMO transmission. As can be seen from FIGS. 9B and 9C,several PAs may be mapped to respective transmission (Tx) antennas. Forexample, provided that the number of transmission (Tx) antennas is setto 2, 2 PAs may be mapped to respective transmission (Tx) antennas. Thesetting of output values (i.e., maximum transmission power) of 2 PAs maybe configured in different ways as shown in FIGS. 9B and 9C.

In FIG. 9B, maximum transmission power (P_(max)) for single antennatransmission may be divisionally applied to PA1 and PA2. That is, if atransmission power value of x [dBm] is assigned to PA1, a transmissionpower value of (P_(max)−x) [dBm] may be applied to PA2. In this case,since total transmission power (P_(max)) is maintained, the transmittermay have higher robustness against the increasing PAPR in the powerlimitation situation.

On the other hand, as can be seen from FIG. 9C, only one Tx antenna(ANT1) may have a maximum transmission power value (P_(max)), and theother Tx antenna (ANT2) may have a half value (P_(max)/2) of the maximumtransmission power value (P_(max)). In this case, only one transmissionantenna may have higher robustness against increasing PAPR.

MIMO System

MIMO technology is not dependent on one antenna path to receive amessage, collects a plurality of data pieces received via severalantennas, and completes total data. As a result, MIMO technology canincrease a data transfer rate within a specific range, or can increase asystem range at a specific data transfer rate. Under this situation,MIMO technology is a next-generation mobile communication technologycapable of being widely applied to mobile communication terminals orRNs. MIMO technology can extend the range of data communication, so thatit can overcome the limited amount of transmission (Tx) data of mobilecommunication systems reaching a critical situation.

FIG. 10A shows the configuration of a general MIMO communication system.Referring to FIG. 10A, if the number of transmit (Tx) antennas increasesto N_(t), and at the same time the number of receive (Rx) antennasincreases to N_(R), a theoretical channel transmission capacity of theMIMO communication system increases in proportion to the number ofantennas, differently from the above-mentioned case in which only atransmitter or receiver uses several antennas, so that transfer rate andfrequency efficiency can be greatly increased. In this case, thetransfer rate acquired by the increasing channel transmission capacitycan theoretically increase by a predetermined amount that corresponds tomultiplication of a maximum transfer rate (R_(o)) acquired when oneantenna is used and a rate of increase (R_(i)). The rate of increase(R_(i)) can be represented by the following equation 1.

R _(i)=min(N _(T) ,N _(R))  [Equation 1]

For example, provided that a MIMO system uses four transmit (Tx)antennas and four receive (Rx) antennas, the MIMO system cantheoretically acquire a high transfer rate which is four times higherthan that of a single antenna system. After the above-mentionedtheoretical capacity increase of the MIMO system was demonstrated in themid-1990s, many developers began to conduct intensive research into avariety of technologies which can substantially increase data transferrate using the theoretical capacity increase. Some of the abovetechnologies have been reflected in a variety of wireless communicationstandards, for example, third-generation mobile communication ornext-generation wireless LAN, etc.

A variety of MIMO-associated technologies have been intensivelyresearched by many companies or developers, for example, research intoinformation theory associated with MIMO communication capacity undervarious channel environments or multiple access environments, researchinto a radio frequency (RF) channel measurement and modeling of the MIMOsystem, and research into a space-time signal processing technology.

Mathematical modeling of a communication method for use in theabove-mentioned MIMO system will hereinafter be described in detail. Ascan be seen from FIG. 10A, it is assumed that there are N_(T) transmit(Tx) antennas and N_(R) receive (Rx) antennas. In the case of atransmission (Tx) signal, a maximum number of transmission informationpieces is N_(T) under the condition that N_(T) transmit (Tx) antennasare used, so that the transmission (Tx) information can be representedby a specific vector shown in the following equation 2.

s=└s ₁ ,s ₂ , . . . ,s _(N) _(T) ┘^(T)  [Equation 2]

In the meantime, individual transmission (Tx) information pieces (s₁,s₂, . . . , s_(NT)) may have different transmission powers. In thiscase, if the individual transmission powers are denoted by (P₁, P₂, . .. , P_(NT)), transmission (Tx) information having an adjustedtransmission power can be represented by a specific vector shown in thefollowing equation 3.

ŝ=[ŝ ₁ ,ŝ ₂ , . . . ,ŝ _(N) _(T) ]^(T) =[P ₁ s ₁ ,P ₂ s ₂ , . . . ,P_(N) _(T) s _(N) _(T) ]^(T)  [Equation 3]

In Equation 3, ŝ is a transmission vector, and can be represented by thefollowing equation 4 using a diagonal matrix P of a transmission (Tx)power.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In the meantime, the information vector ŝ having an adjustedtransmission power is applied to a weight matrix (W), so that N_(T)transmission (Tx) signals (x₁, x₂, . . . , x_(NT)) to be actuallytransmitted are configured. In this case, the weight matrix (W) isadapted to properly distribute transmission (Tx) information toindividual antennas according to transmission channel situations. Theabove-mentioned transmission (Tx) signals (x₁, x₂, . . . , x_(NT)) canbe represented by the following equation 5 using the vector (X).

$\begin{matrix}{x = {{{\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{bmatrix}\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1N_{T}} \\w_{21} & w_{22} & \ldots & w_{2N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 1} & w_{i\; 2} & \ldots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \ldots & w_{N_{T}N_{T}}\end{bmatrix}}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Next, if N_(R) receive (Rx) antennas are used, reception (Rx) signals(y₁, y₂, . . . , y_(NR)) of individual antennas can be represented by aspecific vector (y) shown in the following equation 6.

y=[y ₁ ,y ₂ , . . . ,y _(N) _(R) ]^(T)  [Equation 6]

In the meantime, if a channel modeling is executed in the MIMOcommunication system, individual channels can be distinguished from eachother according to transmit/receive (Tx/Rx) antenna indexes. A specificchannel passing the range from a transmit (Tx) antenna (j) to a receive(Rx) antenna (i) is denoted by h_(ij). In this case, it should be notedthat the index order of the channel h_(ij) is located before a receive(Rx) antenna index and is located after a transmit (Tx) antenna index.

Several channels are tied up, so that they are displayed in the form ofa vector or matrix. An exemplary vector is as follows. FIG. 10B showschannels from N_(T) transmit (Tx) antennas to a receive (Rx) antenna(i).

Referring to FIG. 10B, the channels passing the range from the N_(T)transmit (Tx) antennas to the receive (Rx) antenna (i) can berepresented by the following equation 7.

h _(i) ^(T) =└h _(i1) ,h _(i2) , . . . ,h _(iN) _(T┘)   [Equation 7]

If all channels passing the range from the N_(T) transmit (Tx) antennasto N_(R) receive (Rx) antennas are denoted by the matrix shown inEquation 7, the following equation 8 is acquired.

$\begin{matrix}{H = {\begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\\vdots \\h_{i}^{T} \\\vdots \\h_{N_{R}}^{T}\end{bmatrix} = \begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Additive white Gaussian noise (AWGN) is added to an actual channel whichhas passed the channel matrix (H) shown in Equation 8. The AWGN (n₁, n₂,. . . , n_(NR)) added to each of N_(R) receive (Rx) antennas can berepresented by a specific vector shown in the following equation 9.

n=[n ₁ ,n ₂ , . . . ,n _(N) _(R) ]^(T)  [Equation 9]

A reception signal calculated by the above-mentioned equations can berepresented by the following equation 10.

$\begin{matrix}{y = {\begin{bmatrix}y_{1} \\y_{2} \\\vdots \\y_{i} \\\vdots \\y_{N_{R}}\end{bmatrix} = {{{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{j} \\\vdots \\x_{N_{T}}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\\vdots \\n_{i} \\\vdots \\n_{N_{R}}\end{bmatrix}} = {{Hx} + n}}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

In the meantime, the number of rows and the number of columns of achannel matrix H indicating a channel condition are determined by thenumber of Tx/Rx antennas. In the channel matrix H, the number of rows isequal to the number (N_(R)) of Rx antennas, and the number of columns isequal to the number (N_(T)) of Tx antennas. Namely, the channel matrix His denoted by an N_(R)×N_(T) matrix. Generally, a matrix rank is definedby a smaller number between the number of rows and the number ofcolumns, in which the rows and the columns are independent of eachother. Therefore, the matrix rank cannot be higher than the number ofrows or columns. The rank of the channel matrix H can be represented bythe following equation 11.

rank(H)≦min(N _(T) ,N _(R))  [Equation 11]

A variety of MIMO transmission/reception (Tx/Rx) schemes may be used foroperating the MIMO system, for example, frequency switched transmitdiversity (FSTD), Space Frequency Block Coding (SFBC), Space Time BlockCoding (STBC), Cyclic Delay Diversity (CDD), time switched transmitdiversity (TSTD), etc. In case of Rank 2 or higher, Spatial Multiplexing(SM), Generalized Cyclic Delay Diversity (GCDD), Selective VirtualAntenna Permutation (S-VAP), etc. may be used.

The FSTD scheme serves to allocate subcarriers having differentfrequencies to signals transmitted through multiple antennas so as toobtain diversity gain. The SFBC scheme efficiently applies selectivityof a spatial region and a frequency region so as to obtain diversitygain and multiuser scheduling gain. The STBC scheme applies selectivityof a spatial domain and a time region. The CDD scheme serves to obtaindiversity gain using path delay between transmit antennas. The TSTDscheme serves to temporally divide signals transmitted through multipleantennas. The spatial multiplexing scheme serves to transmit differentdata through different antennas so as to increase a transfer rate. TheGCDD scheme serves to apply selectivity of a time region and a frequencyregion. The S-VAP scheme uses a single precoding matrix and includes aMulti Codeword (MCW) S-VAP for mixing multiple codewords among antennasin spatial diversity or spatial multiplexing and a Single Codeword (SCW)S-VAP using a single codeword.

In case of the STBC scheme from among the above-mentioned MIMOtransmission schemes, the same data symbol is repeated to supportorthogonality in a time domain so that time diversity can be obtained.Similarly, the SFBC scheme enables the same data symbol to be repeatedto support orthogonality in a frequency domain so that frequencydiversity can be obtained. An exemplary time block code used for STBCand an exemplary frequency block code used for SFBC are shown inEquation 12 and Equation 13, respectively. Equation 12 shows a blockcode of the case of 2 transmit (Tx) antennas, and Equation 13 shows ablock code of the case of 4 transmit (Tx) antennas.

$\begin{matrix}{\frac{1}{\sqrt{2}}\begin{pmatrix}S_{1} & S_{2} \\{- S_{2}^{*}} & S_{1}^{*}\end{pmatrix}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack \\{\frac{1}{\sqrt{2}}\begin{pmatrix}S_{1} & S_{2} & 0 & 0 \\0 & 0 & S_{3} & S_{4} \\{- S_{2}^{*}} & S_{1}^{*} & 0 & 0 \\0 & 0 & {- S_{4}^{*}} & S_{3}^{*}\end{pmatrix}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

In Equations 12 and 13, S_(i) (i=1, 2, 3, 4) means a modulated datasymbol. In addition, each row of the matrixes of Equation 12 and 13 mayindicate an antenna port, and each column may indicate time (in case ofSTBC) or frequency (in case of SFBC).

On the other hand, the CDD scheme from among the above-mentioned MIMOtransmission schemes mandatorily increases delay spread so as toincrease frequency diversity. FIGS. 11A and 11B are conceptual diagramsillustrating a general CDD structure for use in the MIMO system. FIG.11A shows a method for applying cyclic delay to a time domain. Ifnecessary, the CDD scheme based on the cyclic delay of FIG. 11A may alsobe implemented as phase-shift diversity of FIG. 11B.

In association with the above-mentioned MIMO transmission techniques,the codebook-based precoding method will hereinafter be described withreference to FIG. 12. FIG. 12 is a conceptual diagram illustratingcodebook-based precoding.

In accordance with the codebook-based precoding scheme, a transceivermay share codebook information including a predetermined number ofprecoding matrixes according to a transmission rank, the number ofantennas, etc. That is, if feedback information is finite, theprecoding-based codebook scheme may be used. The receiver measures achannel state through a reception signal, so that a finite number ofpreferred precoding matrix information (i.e., an index of thecorresponding precoding matrix) may be fed back to the transmitter onthe basis of the above-mentioned codebook information. For example, thereceiver may select an optimum precoding matrix by measuring an ML(Maximum Likelihood) or MMSE (Minimum Mean Square Error) scheme.Although the receiver shown in FIG. 12 transmits precoding matrixinformation for each codeword to the transmitter, the scope or spirit ofthe present invention is not limited thereto.

Upon receiving feedback information from the receiver, the transmittermay select a specific precoding matrix from a codebook on the basis ofthe received information. The transmitter that has selected theprecoding matrix performs a precoding operation by multiplying theselected precoding matrix by as many layer signals as the number oftransmission ranks, and may transmit each precoded Tx signal over aplurality of antennas.

If the receiver receives the precoded signal from the transmitter as aninput, it performs inverse processing of the precoding having beenconducted in the transmitter so that it can recover the reception (Rx)signal. Generally, the precoding matrix satisfies a unitary matrix (U)such as (U*U^(H)=I), so that the inverse processing of theabove-mentioned precoding may be conducted by multiplying a Hermitmatrix (P^(H)) of the precoding matrix H used in the precoding of thetransmitter by the reception (Rx) signal.

Physical Uplink Control Channel (PUCCH)

PUCCH including UL control information will hereinafter be described indetail.

A plurality of UE control information pieces may be transmitted througha PUCCH. When Code Division Multiplexing (CDM) is performed in order todiscriminate signals of UEs, a Constant Amplitude Zero Autocorrelation(CAZAC) sequence having a length of 12 is mainly used. Since the CAZACsequence has a property that a constant amplitude is maintained in atime domain and a frequency domain, a Peak-to-Average Power Ratio (PAPR)of a UE or Cubic Metric (CM) may be decreased to increase coverage. Inaddition, ACK/NACK information for DL data transmitted through the PUCCHmay be covered using an orthogonal sequence.

In addition, control information transmitted through the PUCCH may bediscriminated using cyclically shifted sequences having different cyclicshift values. A cyclically shifted sequence may be generated bycyclically shifting a basic sequence (also called a base sequence) by aspecific cyclic shift (CS) amount. The specific CS amount is indicatedby a CS index. The number of available CSs may be changed according tochannel delay spread. Various sequences may be used as the basicsequence and examples thereof include the above-described CAZACsequence.

PUCCH may include a variety of control information, for example, aScheduling Request (SR), DL channel measurement information, andACK/NACK information for DL data transmission. The channel measurementinformation may include Channel Quality Indicator (CQI), a PrecodingMatrix Index (PMI), and a Rank Indicator (RI).

PUCCH format may be defined according to the type of control informationcontained in a PUCCH, modulation scheme information thereof, etc. Thatis, PUCCH format 1 may be used for SR transmission, PUCCH format 1a or1b may be used for HARQ ACK/NACK transmission, PUCCH format 2 may beused for CQI transmission, and PUCCH format 2a/2b may be used for HARQACK/NACK transmission.

If HARQ ACK/NACK is transmitted alone in an arbitrary subframe, PUCCHformat 1a or 1b may be used. If SR is transmitted alone, PUCCH format 1may be used. The UE may transmit the HARQ ACK/NACK and the SR throughthe same subframe, and a detailed description thereof will hereinafterbe described in detail.

PUCCH format may be summarized as shown in Table 1.

TABLE 1 Number of PUCCH Modulation bits per format scheme subframe Usageetc. 1 N/A N/A SR(Scheduling Request) 1a BPSK 1 ACK/NACK One codeword 1bQPSK 2 ACK/NACK Two codeword 2 QPSK 20 CQI Joint Coding ACK/NACK(extended CP) 2a QPSK + BPSK 21 CQI + ACK/ Normal CP only NACK 2b QPSK +BPSK 22 CQI + ACK/ Normal CP only NACK

FIG. 13 shows a PUCCH resource mapping structure for use in a ULphysical resource block (PRB). N_(RB) ^(UL) is the number of resourceblocks (RBs) for use in uplink (UL), and n_(PRB) is a physical resourceblock (PRB) number. PUCCH may be mapped to both edges of a UL frequencyblock. CQI resources may be mapped to a PRB located just after the edgeof a frequency band, and ACK/NACK may be mapped to this PRB.

PUCCH format 1 is a control channel used for SR transmission. SR(Scheduling Request) may be transmitted in such a manner that SR isrequested or not requested.

PUCCH format 1a/1b is a control channel used for ACK/NACK transmission.In the PUCCH format 1a/1b, a symbol modulated using the BPSK or QPSKmodulation scheme is multiplied by a CAZAC sequence of length 12. Uponcompletion of the CAZAC sequence multiplication, the resultant symbol isblockwise-spread as an orthogonal sequence. A Hadamard sequence oflength 4 is applied to general ACK/NACK information, and a DFT (DiscreteFourier Transform) sequence of length 3 is applied to shortened ACK/NACKinformation and a reference signal (or reference symbol; RS). A Hadamardsequence of length 2 may be applied to the reference signal for theextended CP.

The UE may also transmit HARQ ACK/NACK and SR through the same subframe.For positive SR transmission, the UE may transmit HARQ ACK/NACKinformation through resources allocated for the SR. For negative SRtransmission, the UE may transmit HARQ ACK/NACK information throughresources allocated for ACK/NACK information.

PUCCH format 2/2a/2b will hereinafter be described in detail. PUCCHformat 2/2a/2b is a control channel for transmitting channel measurementfeedback (CQI, PMI, RI).

The PUCCH format 2/2a/2b may support modulation based on a CAZACsequence, and a QPSK-modulated symbol may be multiplied by a CAZACsequence of length 12. Cyclic shift (CS) of the sequence may be changedbetween a symbol and a slot. For a reference signal (RS), orthogonalcovering may be used.

FIG. 14 shows a channel structure of a CQI bit. The CQI bit may includeone or more fields. For example, the CQI bit may include a CQI fieldindicating a CQI index for MCS decision, a PMI field indicating an indexof a precoding matrix of a codebook, and an RI field indicating rank.

Referring to FIG. 14A, a reference signal (RS) may be loaded on twoSC-FDMA symbols spaced apart from each other by a predetermined distancecorresponding to 3 SC-FDMA symbol intervals from among 7 SC-FDMA symbolscontained in one slot, and CQI may be loaded on the remaining 5 SC-FDMAsymbols. The reason why two RSs may be used in one slot is to support ahigh-speed UE. In addition, each UE may be discriminated by a sequence.CQI symbols may be modulated in the entire SC-FDMA symbol, and themodulated CQI symbols may then be transmitted. The SC-FDMA symbol iscomposed of one sequence. That is, a UE performs CQI modulation usingeach sequence, and transmits the modulated result.

The number of symbols that can be transmitted during one TTI is set to10, and CQI modulation is extended up to QPSK. If QPSK mapping isapplied to the SC-FDMA symbol, a CQI value of 2 bits may be loaded onthe SC-FDMA symbol, so that a CQI value of 10 bits may be assigned toone slot. Therefore, a maximum of 20-bit CQI value may be assigned toone subframe. A frequency domain spreading code may be used to spreadCQI in a frequency domain.

CAZAC sequence (for example, a ZC sequence) may be used as a frequencydomain spread code. In addition, another sequence having superiorcorrelation characteristics may be used as the frequency domain spreadcode. Specifically, CAZAC sequences having different cyclic shift (CS)values may be applied to respective control channels, such that theCAZAC sequences may be distinguished from one another. IFFT may beapplied to the frequency domain spread CQI.

FIG. 14B shows the example of PUCCH format 2/2a/2b transmission in caseof the extended CP. One slot includes 6 SC-FDMA symbols. RS is assignedto one OFDM symbol from among 6 OFDM symbols of each slot, and a CQI bitmay be assigned to the remaining 5 OFDM symbols. Except for the sixSC-FDMA symbols, the example of the normal CP of FIG. 14A may be usedwithout change.

Orthogonal covering applied to the RS of FIGS. 14A and 14B is shown inTable 2.

TABLE 2 Normal CP Extended CP [1 1] [1]

Simultaneous transmission of CQI and ACK/NACK information willhereinafter be described with reference to FIG. 15.

In case of the normal CP, CQI and ACK/NACK information can besimultaneously transmitted using PUCCH format 2a/2b. ACK/NACKinformation may be transmitted through a symbol where CQI RS istransmitted. That is, a second RS for use in the normal CP may bemodulated into an ACK/NACK symbol. In the case where the ACK/NACK symbolis modulated using the BPSK scheme as shown in the PUCCH format 1a, CQIRS may be modulated into the ACK/NACK symbol according to the BPSKscheme. In the case where the ACK/NACK symbol is modulated using theQPSK scheme as shown in the PUCCH format 1b, CQI RS may be modulatedinto the ACK/NACK symbol according to the QPSK scheme. On the otherhand, in case of the extended CP, CQI and ACK/NACK information aresimultaneously transmitted using the PUCCH format 2. For this purpose,CQI and ACK/NACK information may be joint-coded.

For details of PUCCH other than the above-mentioned description, the3GPP standard document (e.g., 3GPP TS36.211 5.4) may be referred to, anddetailed description thereof will herein be omitted for convenience ofdescription. However, it should be noted that PUCCH contents disclosedin the above-mentioned standard document can also be applied to a PUCCHused in various embodiments of the present invention without departingfrom the scope or spirit of the present invention.

Channel State Information (CSI) Feedback

In order to correctly perform MIMO technology, the receiver may feedback a rank indicator (RI), a precoding matrix index (PMI) and channelquality indicator (CQI) to the transmitter. RI, PMI and CQI may begenerically named Channel state Information (CSI) as necessary.Alternatively, the term “CQI” may be used as the concept of channelinformation including RI, PMI and CQI.

FIG. 16 is a conceptual diagram illustrating a feedback of channel stateinformation.

Referring to FIG. 16, MIMO transmission data from a transmitter may bereceived at a receiver over a channel (H). The receiver may select apreferred precoding matrix from a codebook on the basis of the receivedsignal, and may feed back the selected PMI to the transmitter. Inaddition, the receiver may measure a Signal-to-Interference plus NoiseRatio (SINR) of the reception (Rx) signal, calculate channel qualityinformation (CQI), and feed back the calculated CQI to the transmitter.In addition, the receiver may feed back a rank indicator (RI) of the Rxsignal to the transmitter. The transmitter may determine the number oflayers suitable for data transmission to the receiver and time/frequencyresources, MCS (Modulation and Coding Scheme), etc. using RI and CQI fedback from the receiver. In addition, the transmitter may transmit theprecoded Tx signal using the precoding matrix (W_(i)) indicated by a PMIfed back from the receiver over a plurality of antennas.

Channel state information will hereinafter be described in detail.

RI is information regarding a channel rank (i.e., the number of layersfor data transmission of a transmitter). RI may be determined by thenumber of allocated Tx layers, and may be acquired from associateddownlink control information (DCI).

PMI is information regarding a precoding matrix used for datatransmission of a transmitter. The precoding matrix fed back from thereceiver may be determined considering the number of layers indicated byRI. PMI may be fed back in case of closed-loop spatial multiplexing (SM)and large delay cyclic delay diversity (CDD). In the case of open-looptransmission, the transmitter may select a precoding matrix according topredetermined rules. A process for selecting a PMI for each rank (rank 1to 4) is as follows. The receiver may calculate a post processing SINRin each PMI, convert the calculated SINR into the sum capacity, andselect the best PMI on the basis of the sum capacity. That is, PMIcalculation of the receiver may be considered to be a process forsearching for an optimum PMI on the basis of the sum capacity. Thetransmitter that has received PMI feedback from the receiver may use aprecoding matrix recommended by the receiver. This fact may be containedas a 1-bit indicator in scheduling allocation information for datatransmission to the receiver. Alternatively, the transmitter may not usethe precoding matrix indicated by a PMI fed back from the transmitter.In this case, precoding matrix information used for data transmissionfrom the transmitter to the receiver may be explicitly contained in thescheduling allocation information. For details of PMI, the 3GPP standarddocument (e.g., 3GPP TS36.211) may be referred to.

CQI is information regarding channel quality. CQI may be represented bya predetermined MCS combination. CQI index may be given as shown in thefollowing table 3.

TABLE 3 CQI index modulation code rate × 1024 efficiency 0 out of range1 QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK 193 0.3770 4 QPSK 308 0.6016 5QPSK 449 0.8770 6 QPSK 602 1.1758 7 16QAM 378 1.4766 8 16QAM 490 1.91419 16QAM 616 2.4063 10 64QAM 466 2.7305 11 64QAM 567 3.3223 12 64QAM 6663.9023 13 64QAM 772 4.5234 14 64QAM 873 5.1152 15 64QAM 948 5.5547

Referring to Table 3, CQI index may be represented by 4 bits (i.e., CQIindexes of 0˜15). Each CQI index may indicate a modulation scheme and acode rate.

A CQI calculation method will hereinafter be described. The followingassumptions (1) to (5) for allowing a UE to calculate a CQI index aredefined in the 3GPP standard document (e.g., 3GPP TS36.213).

(1) The first three OFDM symbols in one subframe are occupied by controlsignaling.

(2) Resource elements (REs) used by a primary synchronization signal, asecondary synchronization signal or a physical broadcast channel (PBCH)are not present.

(3) CP length of a non-MBSFN subframe is assumed.

(4) Redundancy version is set to zero (0).

(5) PDSCH transmission method may be dependent upon a currenttransmission mode (e.g., a default mode) configured in a UE.

(6) The ratio of PDSCH EPRE (Energy Per Resource Element) to acell-specific reference signal EPRE may be given with the exception ofρ_(A). (A detailed description of ρ_(A) may follow the followingassumption. Provided that a UE for an arbitrary modulation scheme may beset to a Transmission Mode 2 having four cell-specific antenna ports ormay be set to a Transmission Mode 3 having an RI of 1 and fourcell-specific antenna ports, ρ_(A) may be denoted byρ_(A)=P_(A)+Δ_(offset)+10 log₁₀ (2) [dB]. In the remaining cases, inassociation with an arbitrary modulation method and the number ofarbitrary layers, ρ_(A) may be denoted by ρ_(A)=P_(A)+Δ_(offset) [dB].Δ_(offset) is given by a nomPDSCH-RS-EPRE-Offset parameter configured byhigher layer signaling.)

Definition of the above-mentioned assumptions (1) to (5) may indicatethat CQI includes not only information regarding channel quality butalso various information of a corresponding UE. That is, different CQIindexes may be fed back according to a throughput or performance of thecorresponding UE at the same channel quality, so that it is necessary todefine a predetermined reference for the above-mentioned assumption.

The UE may receive a downlink reference signal (DL RS) from an eNB, andrecognize a channel state on the basis of the received DL RS. In thiscase, the RS may be a common reference signal (CRS) defined in thelegacy 3GPP LTE system, and may be a Channel state Information ReferenceSignal (CSI-RS) defined in a system (e.g., 3GPP LTE-A system) having anextended antenna structure. The UE may satisfy the assumption given forCQI calculation at a channel recognized through a reference signal (RS),and at the same time calculate a CQI index in which a Block Error Rate(BLER) is not higher than 10%. The UE may transmit the calculated CQIindex to the eNB. The UE may not apply a method for improvinginterference estimation to a CQI index calculation process.

The process for allowing the UE to recognize a channel state anddetermine an appropriate MCS may be defined in various ways in terms ofUE implementation. For example, the UE may calculate a channel state oran effective SINR using a reference signal (RS). In addition, thechannel state or the effective SINR may be measured on the entire systembandwidth (also called ‘Set S’) or may also be measured on somebandwidths (specific subband or specific RB). The CQI for the set S maybe referred to as a Wideband (WB) CQI, and the CQI for some bandwidthsmay be referred to as a subband (SB) CQI. The UE may determine the bestMCS on the basis of the calculated channel state or effective SINR. Thebest MCS may indicate an MCS that satisfies the CQI calculationassumption without exceeding a transport block error rate of 10% duringthe decoding. The UE may determine a CQI index related to the MCS, andmay report the determined CQI index to the eNB.

Further, CQI-only transmission may be considered in which a UE transmitsCQI aperiodically without having data on a PUSCH. Aperiodic CQItransmission may be event-triggered upon receiving a request from theeNB. Such request from the eNB may be a CQI request defined by one bitof DCI format 0. In addition, for CQI-only transmission, MCS index(I_(MCS)) of 29 may be signaled as shown in the following table 4. Inthis case, the CQI request bit of the DCI format 0 is set to 1,transmission of 4 RBs or less may be configured, Redundancy Version 1(RV1) is indicated in PUSCH data retransmission, and a modulation order(Q_(m)) may be set to 2. In other words, in the case of CQI-onlytransmission, only a QPSK (Quadrature Phase Shift Keying) scheme may beused as a modulation scheme.

TABLE 4 Modulation TBS Redundancy MCS Index Order Index Version I_(MCS)Q_(m)′ I_(TBS) rv_(idx) 0 2 0 0 1 2 1 0 2 2 2 0 3 2 3 0 4 2 4 0 5 2 5 06 2 6 0 7 2 7 0 8 2 8 0 9 2 9 0 10 2 10 0 11 4 10 0 12 4 11 0 13 4 12 014 4 13 0 15 4 14 0 16 4 15 0 17 4 16 0 18 4 17 0 19 4 18 0 20 4 19 0 216 19 0 22 6 20 0 23 6 21 0 24 6 22 0 25 6 23 0 26 6 24 0 27 6 25 0 28 626 0 29 reserved 1 30 2 31 3

The CQI reporting operation will hereinafter be described in detail.

In the 3GPP LTE system, when a DL reception entity (e.g., UE) is coupledto a DL transmission entity (e.g., eNB), a Reference Signal ReceivedPower (RSRP) and a Reference Signal Received Quality (RSRQ) that aretransmitted via downlink are measured at an arbitrary time, and themeasured result may be periodically or event-triggeredly reported to theeNB.

In a cellular OFDM wireless packet communication system, each UE mayreport DL channel information based on a DL channel condition viauplink, and the eNB may determine time/frequency resources and MCS(Modulation and Coding Scheme) so as to transmit data to each UE usingDL channel information received from each UE.

In case of the legacy 3GPP LTE system (e.g., 3GPP LTE Release-8 system),such channel information may be composed of Channel Quality Indication(CQI), Precoding Matrix Indicator (PMI), and Rank Indication (RI). Allor some of CQI, PMI and RI may be transmitted according to atransmission mode of each UE. CQI may be determined by the receivedsignal quality of the UE. Generally, CQI may be determined on the basisof DL RS measurement. In this case, a CQI value actually applied to theeNB may correspond to an MCS in which the UE maintains a Block ErrorRate (BLER) of 10% or less at the measured Rx signal quality and at thesame time has a maximum throughput or performance.

In addition, such channel information reporting scheme may be dividedinto periodic reporting and aperiodic reporting upon receiving a requestfrom the eNB.

Information regarding the aperiodic reporting may be assigned to each UEby a CQI request field of 1 bit contained in uplink schedulinginformation sent from the eNB to the UE. Upon receiving the aperiodicreporting information, each UE may transmit channel informationconsidering the UE's transmission mode to the eNB over a physical uplinkshared channel (PUSCH). If necessary, RI and CQI/PMI need not betransmitted over the same PUSCH.

In case of the aperiodic reporting, a cycle in which channel informationis transmitted via a higher layer signal, an offset of the correspondingperiod, etc. may be signaled to each UE in units of a subframe, andchannel information considering a transmission (Tx) mode of each UE maybe transmitted to the eNB over a physical uplink control channel (PUCCH)at intervals of a predetermined time. In the case where UL transmissiondata is present in a subframe in which channel information istransmitted at intervals of a predetermined time, the correspondingchannel information may be transmitted together with data over not aPUCCH but a PUSCH together. In case of the periodic reporting over aPUCCH, a limited number of bits may be used as compared to PUSCH. RI andCQI/PMI may be transmitted over the same PUSCH.

If the periodic reporting collides with the aperiodic reporting in thesame subframe, only the aperiodic reporting may be performed.

In order to calculate a WB CQI/PMI, the latest transmission RI may beused. In a PUCCH reporting mode, RI may be independent of another RI foruse in a PUSCH reporting mode. RI is valid only for CQI/PMI for use inthe corresponding PUSCH reporting mode.

The CQI/PMI/RI feedback type for the PUCCH reporting mode may beclassified into four feedback types (Type 1 to Type 4). Type 1 is CQIfeedback for a user-selected subband. Type 2 is WB CQI feedback and WBPMI feedback. Type 3 is RI feedback. Type 4 is WB CQI feedback.

Referring to Table 5, in the case of periodic reporting of channelinformation, a reporting mode is classified into four reporting modes(Modes 1-0, 1-1, 2-0 and 2-1) according to CQI and PMI feedback types.

TABLE 5 PMI Feedback Type No PMI (OL, TD, single-antenna) Single PMI(CL) CQI Wideband Mode 1-0 Mode 1-1 Feedback RI (only for Open-Loop SM)RI Type One Wideband CQI (4 bit) Wideband CQI (4 bit) when RI > 1, CQIof first codeword Wideband spatial CQI (3 bit) for RI > 1 Wideband PMI(4 bit) UE Mode 2-0 Mode 2-1 Selected RI (only for Open-Loop SM) RIWideband CQI (4 bit) Wideband CQI (4 bit) Best-1 CQI (4 bit) in each BPWideband spatial CQI (3 bit) for RI > 1 Best-1 indicator(L-bit label)Wideband PMI (4 bit) when RI > 1, CQI of first codeword Best-1 CQI (4bit) 1 in each BP Best-1 spatial CQI (3 bit) for RI > 1 Best-1 indicator(L-bit label)

The reporting mode is classified into a wideband (WB) CQI and a subband(SB) CQI according to a CQI feedback type. The reporting mode isclassified into a No-PMI and a Single PMI according to transmission ornon-transmission of PMI. As can be seen from Table 5, ‘NO PMI’ maycorrespond to an exemplary case in which an Open Loop (OL), a TransmitDiversity (TD), and a single antenna are used, and ‘Single PMI” maycorrespond to an exemplary case in which a closed loop (CL) is used.

Mode 1-0 may indicate an exemplary case in which PMI is not transmittedbut only WB CQI is transmitted. In case of Mode 1-0, RI may betransmitted only in the case of OL Spatial Multiplexing (SM), and one WBCQI denoted by 4 bits may be transmitted. If RI is higher than ‘1’, CQIfor a first codeword may be transmitted. In case of Mode 1-0, FeedbackType 3 and Feedback Type 4 may be multiplexed at different time pointswithin the predetermined reporting period, and then transmitted. Theabove-mentioned Mode 1-0 transmission scheme may be referred to as TimeDivision Multiplexing (TDM)-based channel information transmission.

Mode 1-1 may indicate an exemplary case in which a single PMI and a WBCQI are transmitted. In this case, 4-bit WB CQI and 4-bit WB PMI may betransmitted simultaneously with RI transmission. In addition, if RI ishigher than ‘1’, 3-bit WB Spatial Differential CQI may be transmitted.In case of transmission of two codewords, the WB spatial differentialCQI may indicate a differential value between a WB CQI index forCodeword 1 and a WB CQI index for Codeword 2. These differential valuesmay be assigned to the set {−4, −3, −2, −1, 0, 1, 2, 3}, and eachdifferential value may be assigned to any one of values contained in theset and be represented by 3 bits. In case of Mode 1-1, Feedback Type 2and Feedback Type 3 may be multiplexed at different time points withinthe predetermined reporting period, and then transmitted.

Mode 2-0 may indicate that no PMI is transmitted and CQI of aUE-selected band is transmitted. In this case, RI may be transmittedonly in case of open loop spatial multiplexing (OL SM), a WB CQI denotedby 4 bits may be transmitted. In each Bandwidth Part (BP), Best-1 CQImay be transmitted, and Best-1 CQI may be denoted by 4 bits. Inaddition, an indicator of L bits indicating Best-1 may be furthertransmitted. If RI is higher than ‘1’, CQI for a first codeword may betransmitted. In case of Mode 2-0, the above-mentioned feedback type 1,feedback type 3, and feedback type 4 may be multiplexed at differenttime points within a predetermined reporting period, and thentransmitted.

Mode 2-1 may indicate an exemplary case in which a single PMI and CQI ofa UE-selected band are transmitted. In this case, WB CQI of 4 bits, WBspatial differential CQI of 3 bits, and WB PMI of 4 bits are transmittedsimultaneously with RI transmission. In addition, Best-1 CQI of 4 bitsand a Best-1 indicator of L bits may be simultaneously transmitted ateach bandwidth part (BP). If RI is higher than ‘1’, Best-1 spatialdifferential CQI of 3 bits may be transmitted. During transmission oftwo codewords, a differential value between a Best-1 CQI index ofCodeword 1 and a Best-1 CQI index of Codeword 2 may be indicated. InMode 2-1, the above-mentioned feedback type 1, feedback 2, and feedbacktype 3 may be multiplexed at different time points within apredetermined reporting period, and then transmitted.

In the UE selected SB CQI reporting mode, the size of BP (BandwidthPart) subband may be defined by the following table 6.

TABLE 6 System Bandwidth Subband Size k Bandwidth Parts N_(RB) ^(DL)(RBs) (J) 6-7 NA NA  8-10 4 1 11-26 4 2 27-63 6 3  64-110 8 4

Table 6 shows a bandwidth part (BP) configuration and the subband sizeof each BP according to the size of a system bandwidth. A UE may selecta preferred subband within each BP, and calculate CQI for thecorresponding subband. In Table 6, if the system bandwidth is set to 6or 7, this means no application of both the subband size and the numberof bandwidth parts (BPs). That is, the system bandwidth of 6 or 7 meansapplication of only WB CQI, no subband state, and a BP of 1.

FIG. 17 shows an example of a UE selected CQI reporting mode. N_(RB)^(DL) is the number of RBs of the entire bandwidth. The entire bandwidthmay be divided into N CQI subbands (1, 2, 3, . . . , N). One CQI subbandmay include k RBs defined in Table 6. If the number of RBs of the entirebandwidth is not denoted by an integer multiple of k, the number of RBscontained in the last CQI subband (i.e., the N-th CQI subband) may bedetermined by the following equation 14.

N _(RB) ^(DL) −k·└N _(RB) ^(DL) /k┘  [Equation 14]

In Equation 14, └ ┘ represents a floor operation, and └x┘ or floor(x)represents a maximum integer not higher than ‘x’. In addition, N_(J) CQIsubbands construct one BP, and the entire bandwidth may be divided intoJ BPs. UE may calculate a CQI index for one preferred Best-1 CQI subbandcontained in one BP, and transmit the calculated CQI index over a PUCCH.In this case, a Best-1 indicator indicating which Best-1 CQI subband isselected from one BP may also be transmitted. The Best-1 indicator maybe composed of L bits, and L may be represented by the followingequation 15.

L=┌log₂ N _(J)┐  [Equation 15]

In Equation 15, ┌ ┐ represents a ceiling operation, and ┌x┐ orceiling(x) represents a minimum integer not higher than ‘x’.

In the above-mentioned UE selected CQI reporting mode, a frequency bandfor CQI index calculation may be determined Hereinafter, a CQItransmission cycle will hereinafter be described in detail.

Each UE may receive information composed of a combination of atransmission cycle of channel information and an offset from an upperlayer through RRC signaling. The UE may transmit channel information toan eNB on the basis of the received channel information transmissioncycle information.

FIG. 18 is a conceptual diagram illustrating a method for enabling a UEto periodically transmit channel information. For example, if a UEreceives combination information in which a channel informationtransmission cycle is set to 5 and an offset is set to 1, the UEtransmits channel information in units of 5 subframes, one subframeoffset is assigned in the increasing direction of a subframe index onthe basis of the 0^(th) subframe, and channel information may betransmitted over a PUCCH. In this case, the subframe index may becomprised of a combination of a system frame number (n_(f)) and 20 slotindexes (n_(s), 0˜19) present in the system frame. One subframe may becomprised of 2 slots, such that the subframe index may be represented by10×n_(f)+floor(n_(s)/2).

One type for transmitting only WB CQI and the other type fortransmitting both WB CQI and SB CQI may be classified according to CQIfeedback types. In case of the first type for transmitting only the WBCQI, WB CQI information for the entire band is transmitted at a subframecorresponding to each CQI transmission cycle. The WB periodic CQIfeedback transmission cycle may be set to any of 2, 5, 10, 16, 20, 32,40, 64, 80, or 160 ms or no transmission of the WB periodic CQI feedbacktransmission cycle may be established. In this case, if it is necessaryto transmit PMI according to the PMI feedback type of Table 5, PMIinformation is transmitted together with CQI. In case of the second typefor transmitting both WB CQI and SB CQI, WB CQI and SB CQI may bealternately transmitted.

FIG. 19 is a conceptual diagram illustrating a method for transmittingboth WB CQI and SB CQI according to an embodiment of the presentinvention. FIG. 19 shows an exemplary system comprised of 16 RBs. If asystem frequency band is comprised of 16 RBs, for example, it is assumedthat two bandwidth parts (BPs) (BP0 and BP1) may be configured, each BPmay be composed of 2 subbands (SBs) (SB0 and SB1), and each SB may becomposed of 4 RBs. In this case, as previously stated in Table 6, thenumber of BPs and the size of each SB are determined according to thenumber of RBs contained in the entire system band, and the number of SBscontained in each BP may be determined according to the number of RBs,the number of BPs and the size of SB.

In case of the type for transmitting both WB CQI and SB CQI, the WB CQIis transmitted in the CQI transmission subframe. In the nexttransmission subframe, CQI of one SB (i.e., Best-1) having a goodchannel state from among SB0 and SB1 at BP0 and an index (i.e., Best-1indicator) of the corresponding SB are transmitted. In the further nexttransmission subframe, CQI of one SB (i.e., Best-1) having a goodchannel state from among SB0 and SB1 at BP1 and an index (i.e., Best-1indicator) of the corresponding SB are transmitted. After transmittingthe WB CQI, CQI of individual BPs are sequentially transmitted. In thiscase, CQI of a BP located between a first WB CQI transmitted once and asecond WB CQI to be transmitted after the first WB CQI may besequentially transmitted one to four times. For example, if the CQI ofeach BP is transmitted once during a time interval between two WB CQIs,CQIs may be transmitted in the order of WB CQI→BP0 CQI→BP1 CQI→WB CQI.In another example, if the CQI of each BP is transmitted four timesduring a time interval between two WB CQIs, CQIs may be transmitted inthe order of WB CQI→BP0 CQI→BP1 CQI→BP0 CQI→BP1 CQI→BP0 CQI→BP1 CQI→BP0CQI→BP1 CQI→WB CQI. Information about the number of sequentialtransmission times of BP CQI during a time interval between two WB CQIsis signaled through a higher layer. Irrespective of WB CQI or SB CQI,the above-mentioned information about the number of sequentialtransmission times of BP CQI may be transmitted through a PUCCH in asubframe corresponding to information of a combination of channelinformation transmission cycle signaled from the higher layer and anoffset of FIG. 18.

In this case, if PMI also needs to be transmitted according to the PMIfeedback type, PMI information and CQI must be simultaneouslytransmitted. If PUSCH for UL data transmission is present in thecorresponding subframe, CQI and PMI can be transmitted along with datathrough PUSCH instead of PUCCH.

FIG. 20 is a conceptual diagram illustrating an exemplary CQItransmission scheme when both WB CQI and SB CQI are transmitted. In moredetail, provided that combination information in which a channelinformation transmission cycle is set to 5 and an offset is set to 1 issignaled as shown in FIG. 18, and BP information between two WB CQI/PMIparts is sequentially transmitted once, FIG. 20 shows the example ofchannel information transmission operation of a UE.

On the other hand, in case of RI transmission, RI may be signaled byinformation of a combination of one signal indicating how many WBCQI/PMI transmission cycles are used for RI transmission and an offsetof the corresponding transmission cycle. In this case, the offset may bedefined as a relative offset for a CQI/PMI transmission offset. Forexample, provided that an offset of the CQI/PMI transmission cycle isset to 1 and an offset of the RI transmission cycle is set to zero, theoffset of the RI transmission cycle may be identical to that of theCQI/PMI transmission cycle. The offset of the RI transmission cycle maybe defined as a negative value or zero.

FIG. 21 is a conceptual diagram illustrating transmission of WB CQI, SBCQI and RI. In more detail, FIG. 21 shows that, under CQI/PMItransmission of FIG. 20, an RI transmission cycle is one time the WBCQI/PMI transmission cycle and the offset of RI transmission cycle isset to ‘−1’. Since the RI transmission cycle is one time the WB CQI/PMItransmission cycle, the RI transmission cycle has the same time cycle. Arelative difference between the RI offset value ‘−1’ and the CQI offset‘1’ of FIG. 20 is set to ‘−1’, such that RI can be transmitted on thebasis of the subframe index ‘0’.

In addition, provided that RI transmission overlaps with WB CQI/PMItransmission or SB CQI/PMI transmission, WB CQI/PMI or SB CQI/PMI maydrop. For example, provided that the RI offset is set to ‘0’ instead of‘−1’, the WB CQI/PMI transmission subframe overlaps with the RItransmission subframe. In this case, WB CQI/PMI may drop and RI may betransmitted.

By the above-mentioned combination, CQI, PMI, and RI may be transmitted,and such information may be transmitted from each UE by RRC signaling ofa higher layer. The eNB may transmit appropriate information to each UEin consideration of a channel situation of each UE and a distributionsituation of UEs included in the eNB.

Meanwhile, payload sizes of SB CQI, WB CQI/PMI, RI and WB CQI inassociation with the PUCCH report type may be represented by thefollowing table 7.

TABLE 7 PUCCH PUCCH Reporting Modes Report Mode 1-1 Mode 2-1 Mode 1-0Mode 2-0 Type Reported Mode State (bits/BP) (bits/BP) (bits/BP)(bits/BP) 1 Sub-band RI = 1 NA 4 + L NA 4 + L CQI RI > 1 NA 7 + L NA 4 +L 2 Wideband 2 TX Antennas RI = 1 6 6 NA NA CQI/PMI 4 TX Antennas RI = 18 8 NA NA 2 TX Antennas RI > 1 8 8 NA NA 4 TX Antennas RI > 1 11 11 NANA 3 RI 2-layer spatial multiplexing 1 1 1 1 4-layer spatialmultiplexing 2 2 2 2 4 Wideband RI = 1 or RI > 1 NA NA 4 4 CQI

Aperiodic transmission of CQI, PMI and RI over a PUSCH will hereinafterbe described.

In case of the aperiodic reporting, RI and CQI/PMI may be transmittedover the same PUSCH. In case of the aperiodic reporting mode, RIreporting is valid only for CQI/PMI reporting in the correspondingaperiodic reporting mode. CQI-PMI combinations capable of beingsupported to all the rank values are shown in the following table 8.

TABLE 8 PMI Feedback Type No PMI (OL, TD, single-antenna) with PMI (CL)PUSCH CQI Wideband Mode 1-2: Multiple PMI Feedback Type (Wideband CQI)RI 1^(st) Wideband CQI (4 bit) 2^(nd) Wideband CQI (4 bit) if RI >1subband PMIs on each subband UE Selected Mode 2-0 Mode 2-2: Multiple PMI(Subband CQI) RI (only for Open-Loop SM) RI Wideband CQI (4 bit) +Best-M CQI (2 bit) 1^(st) Wideband CQI (4 bit) + Best-M CQI (2 bit)Best-M index 2^(nd) Wideband CQI (4 bit) + Best-M CQI (2 bit) whenRI >1, CQI of first codeword if RI >1 Wideband PMI + Best-M PMI Best-Mindex Higher layer-configured Mode 3-0 Mode 3-1: Single PMI (subbandCQI) RI (only for Open-Loop SM) RI Wideband CQI (4 bit) + subband CQI (2bit) 1^(st) Wideband CQI (4 bit) + subband CQI when RI >1, CQI of firstcodeword (2 bit) 2^(nd) Wideband CQI (4 bit) + subband CQI (2 bit) ifRI >1 Wideband PMI

Mode 1-2 of Table 8 indicates a WB feedback. In Mode 1-2, a preferredprecoding matrix for each subband may be selected from a codebook subseton the assumption of transmission only in the corresponding subband. TheUE may report one WB CQI at every codeword, and WB CQI may be calculatedon the assumption that data is transmitted on subbands of the entiresystem bandwidth (Set S) and the corresponding selected precoding matrixis used on each subband. The UE may report the selected PMI for eachsubband. In this case, the subband size may be given as shown in thefollowing table 9. In Table 9, if the system bandwidth is set to 6 or 7,this means no application of the subband size. That is, the systembandwidth of 6 or 7 means application of only WB CQI and no subbandstate.

TABLE 9 System Bandwidth Subband Size N_(RB) ^(DL) (k) 6-7 NA  8-10 411-26 4 27-63 6  64-110 8

In Table 8, Mode 3-0 and Mode 3-1 show a subband feedback configured bya higher layer.

In Mode 3-0, the UE may report a WB CQI value calculated on theassumption of data transmission on the set-S (total system bandwidth)subbands. The UE may also report one subband CQI value for each subband.The subband CQI value may be calculated on the assumption of datatransmission only at the corresponding subband. Even in the case ofRI>1, WB CQI and SB CQI may indicate a channel quality for Codeword 1.

In Mode 3-1, a single precoding matrix may be selected from a codebooksubset on the assumption of data transmission on the set-S subbands. TheUE may report one SB CQI value for each codeword on each subband. The SBCQI value may be calculated on the assumption of a single precodingmatrix used in all subbands and data transmission on the correspondingsubband. The UE may report a WB CQI value for each codeword. The WB CQIvalue may be calculated on the assumption of a single precoding matrixused in all the subbands and data transmission on the set-S subbands.The UE may report one selected precoding matrix indicator. The SB CQIvalue for each codeword may be represented by a differential WB CQIvalue using a 2-bit subband differential CQI offset. That is, thesubband differential CQI offset may be defined as a differential valuebetween a SB CQI index and a WB CQI index. The subband differential CQIoffset value may be assigned to any one of four values {−2, 0, +1, +2}.In addition, the subband size may be given as shown in the followingtable 9.

In Table 8, Mode 2-0 and Mode 2-2 illustrate a UE selected subbandfeedback. Mode 2-0 and Mode 2-2 illustrate reporting of best-M averages.

In Mode 2-0, the UE may select the set of M preferred subbands (i.e.,best-M) from among the entire system bandwidth (set S). The size of onesubband may be given as k, and k and M values for each set-S range maybe given as shown in the following table 10. In Table 10, if the systembandwidth is set to 6 or 7, this means no application of both thesubband size and the M value. That is, the system bandwidth of 6 or 7means application of only WB CQI and no subband state.

The UE may report one CQI value reflecting data transmission only at thebest-M subbands. This CQI value may indicate a channel quality forCodeword 1 even in the case of RI>1. In addition, the UE may report a WBCQI value calculated on the assumption of data transmission on the set-Ssubbands. The WB CQI value may indicate a channel quality for Codeword 1even in the case of RI>1.

TABLE 10 System Bandwidth N_(RB) ^(DL) Subband Size k (RBs) M 6-7 NA NA 8-10 2 1 11-26 2 3 27-63 3 5  64-110 4 6In Mode 2-2, the UE may select the set of M preferred subbands (i.e.,best-M) from among the set-S subbands (where the size of one subband isset to k). Simultaneously, one preferred precoding matrix may beselected from among a codebook subset to be used for data transmissionon the M selected subbands. The UE may report one CQI value for eachcodeword on the assumption that data transmission is achieved on Mselected subbands and selection precoding matrices are used in each ofthe M subbands. The UE may report an indicator of one precoding matrixselected for the M subbands. In addition, one precoding matrix (i.e., aprecoding matrix different from the precoding matrix for theabove-mentioned M selected subbands) may be selected from among thecodebook subset on the assumption that data transmission is achieved onthe set-S subbands. The UE may report WB CQI, which is calculated on theassumption that data transmission is achieved on the set-S subbands andone precoding matrix is used in all the subbands, for every codeword.The UE may report an indicator of the selected one precoding matrix inassociation with all subbands.

In association with entirety of UE-selected subband feedback modes (Mode2-0 and Mode 2-2), the UE may report the positions of M selectedsubbands using a combination index (r), where r may be represented bythe following equation 16.

$\begin{matrix}{r = {\sum\limits_{i = 0}^{M - 1}{\langle\begin{matrix}{N - s_{i}} \\{M - i}\end{matrix}\rangle}}} & \left\lbrack {{Equation}\mspace{14mu} 16} \right\rbrack\end{matrix}$

In Equation 16, the set {s_(i)}_(i=0) ^(M-1), (1≦s_(i)≦N, s_(i)<s_(i+1))may include M sorted subband indexes. In Equation 16,

${\langle\begin{matrix}x \\y\end{matrix}\rangle}\quad$

may indicate an extended binomial coefficient, which is set to

$\begin{pmatrix}x \\y\end{pmatrix}\quad$

in case of x≧y and is set to zero (0) in case of x<y. Therefore, r mayhave a unique label and may be denoted by

$r \in {\left\{ {0,\ldots \mspace{14mu},{\begin{pmatrix}N \\M\end{pmatrix} - 1}} \right\}.}$

In addition, a CQI value for M selected subbands for each codeword maybe denoted by a relative differential value in association with WB CQI.The relative differential value may be denoted by a differential CQIoffset level of 2 bits, and may have a value of ‘CQI index—WB CQI index’of M selected subbands. An available differential CQI value may beassigned to any one of four values {+1, +2, +3, +4}.

In addition, the size (k) of supported subbands and the M value may begiven as shown in Table 10. As shown in Table 10, k or M may be given asa function of a system bandwidth.

A label indicating the position of each of M selected subbands (i.e.,best-M subbands) may be denoted by L bits, where L is denoted by

$L = {\left\lceil {\log_{2}\begin{pmatrix}N \\M\end{pmatrix}} \right\rceil.}$

Precoder for 8 Tx Antennas

A system having an extended antenna configuration (e.g. a 3GPP LTERelease-10 system) may perform MIMO transmission, for example, through 8Tx antennas. Thus a codebook for supporting 8Tx MIMO transmission needsto be designed.

To report CSI regarding channels transmitted through 8 antenna ports,codebooks illustrated in Table 11 to Table 18 may be used. 8 CSI antennaports may be labeled with antenna port 15 to antenna port 22. Table 11illustrates an exemplary codebook for a 1-layer CSI report using antennaport 15 to antenna port 22. Table 12 illustrates an exemplary codebookfor a 2-layer CSI report using antenna port 15 to antenna port 22. Table13 illustrates an exemplary codebook for a 3-layer CSI report usingantenna port 15 to antenna port 22. Table 14 illustrates an exemplarycodebook for a 4-layer CSI report using antenna port 15 to antenna port22. Table 15 illustrates an exemplary codebook for a 5-layer CSI reportusing antenna port 15 to antenna port 22. Table 16 illustrates anexemplary codebook for a 6-layer CSI report using antenna port 15 toantenna port 22. Table 17 illustrates an exemplary codebook for a7-layer CSI report using antenna port 15 to antenna port 22. Table 18illustrates an exemplary codebook for an 8-layer CSI report usingantenna port 15 to antenna port 22.

In Table 11 to Table 18, φ_(n) and v_(m) may be given as Equation 17.

φ_(n) =e ^(jπn/2)

v _(m)=[1e ^(j2πm/32) e ^(j4πm/32) e ^(j6πm/32)]^(T)  [Equation 17]

TABLE 11 i₂ i₁  0  1  2  3 0-15 W_(2i) ₁ _(,0) ⁽¹⁾ W_(2i) ₁ _(,1) ⁽¹⁾W_(2i) ₁ _(,2) ⁽¹⁾ W_(2i) ₁ _(,3) ⁽¹⁾ i₂ i₁  4  5  6  7 0-15 W_(2i) ₁_(+1,0) ⁽¹⁾ W_(2i) ₁ _(+1,1) ⁽¹⁾ W_(2i) ₁ _(+1,2) ⁽¹⁾ W_(2i) ₁ _(+1,3)⁽¹⁾ i₂ i₁  8  9 10 11 0-15 W_(2i) ₁ _(+2,0) ⁽¹⁾ W_(2i) ₁ _(+2,1) ⁽¹⁾W_(2i) ₁ _(+2,2) ⁽¹⁾ W_(2i) ₁ _(+2,3) ⁽¹⁾ i₂ i₁ 12 13 14 15 0-15 W_(2i)₁ _(+3,0) ⁽¹⁾ W_(2i) ₁ _(+3,1) ⁽¹⁾ W_(2i) ₁ _(+3,2) ⁽¹⁾ W_(2i) ₁ _(+3,3)⁽¹⁾${{where}\mspace{14mu} W_{m,n}^{(1)}} = {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} \\{\phi_{n}v_{m}}\end{bmatrix}}$

TABLE 12 i₂ i₁ 0 1 2 3 0-15 W_(2i) ₁ _(,2i) ₁ _(,0) ⁽²⁾ W_(2i) ₁ _(,2i)₁ _(,1) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+1,0) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+1,1)⁽²⁾ i₂ i₁ 4 5 6 7 0-15 W_(2i) ₁ _(+2,2i) ₁ _(+2,0) ⁽²⁾ W_(2i) ₁ _(+2,2i)₁ _(+2,1) ⁽²⁾ W_(2i) ₁ _(+3,2i) ₁ _(+3,0) ⁽²⁾ W_(2i) ₁ _(+3,2i) ₁_(+3,1) ⁽²⁾ i₂ i₁ 8 9 10 11 0-15 W_(2i) ₁ _(,2i) ₁ _(+1,0) ⁽²⁾ W_(2i) ₁_(,2i) ₁ _(+1,1) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+2,0) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁_(+2,1) ⁽²⁾ i₂ i₁ 12 13 14 15 0-15 W_(2i) ₁ _(,2i) ₁ _(+3,0) ⁽²⁾ W_(2i)₁ _(,2i) ₁ _(+3,1) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+3,0) ⁽²⁾ W_(2i) ₁ _(+1,2i)₁ _(+3,1) ⁽²⁾${{where}\mspace{14mu} W_{m,m^{\prime},n}^{(2)}} = {{\frac{1}{4}\begin{bmatrix}v_{m} & v_{m^{\prime}} \\{\phi_{n}v_{m}} & {{- \phi_{n}}v_{m^{\prime}}}\end{bmatrix}}.}$

TABLE 13 i₂ i₁  0  1  2 0-3 W_(8i) ₁ _(,8i) ₁ _(,8i) ₁ ₊₈ ⁽³⁾ W_(8i) ₁_(+8,8i) ₁ _(,8i) ₁ ₊₈ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(,8i) ₁ _(+8,8i) ₁₊₈ ⁽³⁾ i₂ i₁  3  4  5 0-3 {tilde over (W)}_(8i) ₁ _(+8,8i) ₁ _(,8i) ₁⁽²⁾ W_(8i) ₁ _(+2,8i) ₁ _(+2,4i) ₁ ₊₁₀ ⁽³⁾ W_(8i) ₁ _(+10,8i) ₁ _(+2,8i)₁ ₊₁₀ ⁽³⁾ i₂ i₁  6  7  8 0-3 {tilde over (W)}_(8i) ₁ _(+2,8i) ₁_(+10,8i) ₁ ₊₁₀ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+10,8i) ₁ _(+2,8i) ₁ ₊₂⁽³⁾ W_(8i) ₁ _(+4,8i) ₁ _(+4,8i) ₁ ₊₁₂ ⁽³⁾ i₂ i₁  9 10 11 0-3 W_(8i) ₁_(+12,8i) ₁ _(+4,8i) ₁ ₊₁₂ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+4,8i) ₁_(+12,8i) ₁ ₊₁₂ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+12,8i) ₁ _(+4,8i) ₁ ₊₄⁽³⁾ i₂ i₁ 12 13 0-3 W_(8i) ₁ _(+6,8i) ₁ _(+6,8i) ₁ ₊₁₄ ⁽³⁾ W_(8i) ₁_(+14,8i) ₁ _(+6,8i) ₁ ₊₁₄ ⁽³⁾ i₂ i₁ 14 15 0-3 {tilde over (W)}_(8i) ₁_(+6,8i) ₁ _(+14,8i) ₁ ₊₁₄ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+14,8i) ₁_(+6,8i) ₁ ₊₆ ⁽³⁾${{{where}\mspace{14mu} W_{m,m^{\prime},m^{''}}^{(3)}} = {\frac{1}{\sqrt{24}}\begin{bmatrix}v_{m} & v_{m^{\prime}} & v_{m^{''}} \\v_{m} & {- v_{m^{\prime}}} & {- v_{m^{''}}}\end{bmatrix}}},$${\overset{\sim}{W}}_{m,m^{\prime},m^{''}}^{(3)} = {\frac{1}{\sqrt{24}}\begin{bmatrix}v_{m} & v_{m^{\prime}} & v_{m^{''}} \\v_{m} & v_{m^{\prime}} & {- v_{m^{''}}}\end{bmatrix}}$

TABLE 14 i₂ i₁ 0 1 2 3 0-3 W_(8i) ₁ _(,8i) ₁ _(+8,0) ⁽⁴⁾ W_(8i) ₁ _(,8i)₁ _(+8,1) ⁽⁴⁾ W_(8i) ₁ _(+2,8i) ₁ _(+10,0) ⁽⁴⁾ W_(8i) ₁ _(+2,8i) ₁_(+10,1) ⁽⁴⁾ i₂ i₁ 4 5 6 7 0-3 W_(8i) ₁ _(+4,8i) ₁ _(+12,0) ⁽⁴⁾ W_(8i) ₁_(+4,8i) ₁ _(+12,1) ⁽⁴⁾ W_(8i) ₁ _(+6,8i) ₁ _(+14,0) ⁽⁴⁾ W_(8i) ₁_(+6,8i) ₁ _(+14,1) ⁽⁴⁾${{where}\mspace{14mu} W_{m,m^{\prime},n}^{(4)}} = {\frac{1}{\sqrt{32}}\begin{bmatrix}v_{m} & v_{m^{\prime}} & v_{m} & v_{m^{\prime}} \\{\phi_{n}v_{m}} & {\phi_{n}v_{m^{\prime}}} & {{- \phi_{n}}v_{m}} & {{- {\phi_{n}}^{\prime}}v_{m^{\prime}}}\end{bmatrix}}$

TABLE 15 i₂ i₁ 0 0-3$W_{i_{1}}^{(5)} = {\frac{1}{\sqrt{40}}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16}\end{bmatrix}}$

TABLE 16 i₂ i₁ 0 0-3$W_{i_{1}}^{(6)} = {\frac{1}{\sqrt{48}}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 16} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16} & {- v_{{2i_{1}} + 16}}\end{bmatrix}}$

TABLE 17 i₂ i₁ 0 0-3$W_{i_{1}}^{(7)} = {\frac{1}{\sqrt{56}}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 24} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16} & {- v_{{2i_{1}} + 16}} & v_{{2i_{1}} + 24}\end{bmatrix}}$

TABLE 18 i₂ i₁ 0 0 $W_{i_{1}}^{(8)} = {\frac{1}{8}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 24} & v_{{2i_{1}} + 24} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16} & {- v_{{2i_{1}} + 16}} & v_{{2i_{1}} + 24} & {- v_{{2i_{1}} + 24}}\end{bmatrix}}$

As described above, period feedback information transmission can beperformed through a PUCCH and aperiodic feedback informationtransmission can be performed through a PUSCH. As recommended by thepresent invention, precoding information can be represented by acombination of PMI_(—)1 and PMI_(—)2. PMI_(—)1 and PMI_(—)2 may berespectively represented by weight matrices W1 (or i1) and W2 (or i2).When overall precoding information is composed of a combination of twodifferent precoding information pieces, various transmission modes canbe configured according to a scheme of transmitting PMI_(—)1 andPMI_(—)2 (frequency granularity, transmission timing, etc.) for feedbackinformation transmission.

In aperiodic PUSCH transmission, one report can include both PMI_(—)1and PMI_(—)2. If one of PMI_(—)1 and PMI_(—)2 is fixed (i.e., one ofPMI_(—)1 and PMI_(—)2 has a predetermined value), one report may includeonly PMI_(—)2 or PMI_(—)1. Even in this case, the entire PMI isdetermined by a combination of PMI_(—)1 and PMI_(—)2. In addition, RIand CQI may be included with PMI_(—)1 and PMI_(—)2 in one report.

In periodic PUCCH transmission, a transmission scheme for signalingPMI_(—)1 and PMI_(—)2 at different time points (different subframes) maybe considered. In this case, PMI_(—)2 may be information regarding WB orSB. In aperiodic PUCCH transmission, a transmission scheme fordetermining a PMI from one report (through one subframe) may beconsidered. In this case, one of PMI_(—)1 and PMI_(—)2 is fixed (i.e.,one of PMI_(—)1 and PMI_(—)2 has a predetermined value) and need not besignaled. When one of PMI_(—)1 and PMI_(—)2 is not fixed, it is notnecessary to signal the non-fixed one of PMI_(—)1 and PMI_(—)2. Even inthis case, the entire PMI is determined by a combination of PMI_(—)1 andPMI_(—)2. PMI_(—)2 may be information regarding WB. In PUCCHtransmission, various PUCCH feedback transmission modes can beconfigured according to an RI and CQI transmission scheme (frequencygranularity, transmission timing, etc.).

Transmission of Feedback Information on PUCCH

Feedback information that a receiver transmits to a transmitter forreliable MIMO transmission may include an RI, a PMI, CQI, an ACK/NACK,an SR, etc. An RI, a PMI, CQI, etc. may be used as channel informationfor data transmission. To feedback channel information in a systemsupporting extended multi-antenna transmission, a feedback informationreporting scheme may be configured based on feedback modes defined inthe legacy 3GPP LTE Release-8 system (e.g. the feedback modes describedbefore in relation to Table 5). First of all, conventional feedbackmodes will be described in brief.

The properties of reported feedback information may be classified intoshort term and long term in terms of time and SB and WB in terms offrequency. Specifically, an RI is long-term WB information. A PMIindicating a precoding matrix that represents the long-term covarianceof a channel is long-term WB information and a PMI reported in a shortterm is short-term WB or short-term SB information. CQI may be reportedmore often than an RI and may be classified as SB CQI or WB CQIaccording to a reported frequency granularity.

In the 3GPP LTE Release-8 system, channel information may be transmittedaccording to transmission time points as illustrated in Table 19.

TABLE 19 T_1 T_2 T_3~T_N Mode 1-0 RI Wideband CQI Mode 2-0 RI WidebandCQI Best-1 CQI in each BP Mode 1-1 RI Wideband CQI Wideband PMI Mode 2-1RI Wideband CQI Best-1 CQI in each BP Wideband PMIIn Mode 1-0, an RI is reported in an uplink transmission subframe T_(—)1and then WB CQI is reported in another uplink transmission subframeT_(—)2. The RI and the WB CQI are reported periodically and thereporting period of the RI is a multiple of that of the WB CQI. Aspecific offset may be set between the subframe T_(—)1 carrying the RIand the subframe T_(—)2 carrying the WB CQI and the offset may be 0 atminimum. In Mode 2-0, SB CQI transmission is added to Mode 1-0. An SB isselected from a specific BP and CQI for the selected SB is reported asSB CQI. Mode 1-1 and Mode 2-1 are cases where PMI transmission is addedto Mode 1-0 and Mode 2-0, respectively. The PMI is a WB PMI which istransmitted along with WB CQI.

The system supporting an extended antenna configuration (e.g. the 3GPPLTE-A system) may use different precoding matrices in configuringprecoding weights. As the receiver reports an index indicating eachprecoding matrix, the transmitter may configure a precoding weight for achannel. For example, to configure a feedback codebook including twodifferent precoding matrices, indexes included in the respectiveprecoding matrices may be reported. The indexes may be referred to asPMI_(—)1 and PMI_(—)2, respectively. PMI_(—)1 may be a precoding weightreflecting long-term fading and PMI_(—)2 may be a precoding weightreflecting short-term fading. For example, PMI_(—)1 indicating along-term covariance matrix like a channel covariance matrix may bereported less frequently and may be expressed as a value that does notsubstantially change (an almost same value) in a WB. Accordingly,PMI_(—)1 may be reported in the same period as that of an RI. On theother hand, PMI_(—)2 reflecting short-term fading is reported morefrequently. If PMI_(—)2 applies to a WB, it may be reported in a similarperiod to that of WB CQI. If PMI_(—)2 applies to an SB, it may bereported at a reporting position of each SB CQI.

Reported PMI and CQI may have different values according to a rank. Ifthe size of each piece of the PMI and CQI is known, the number ofdecodings may be reduced, thereby increasing system performance.Therefore, if a time or frequency is allocated for transmitting an RI onan uplink transmission channel, information for decoding PMI and CQI maybe acquired after RI information is first interpreted. Therefore,PMI_(—)1 reported in a long term is preferably transmitted at adifferent time point or in a different frequency from an RI.

Now, specific examples of feedback information transmission timingaccording to the present invention will be described.

In an example, PMI_(—)1 may be a WB PMI and transmitted in the sameperiod as an RI. The reporting timing of PMI_(—)1 may have a specificoffset with respect to that of an RI. The offset may be 1 at minimum.That is, PMI_(—)1 may be reported after the RI, rather than PMI_(—)1 andthe RI are transmitted simultaneously.

In another example, the transmission period of PMI_(—)1 may be set to beshorter than that of the RI and longer than PMI_(—)2. That is, PMI_(—)1is transmitted more frequently than the RI and less frequently thanPMI_(—)2.

In a third example, PMI_(—)1 and the RI may be transmitted together. Inthis case, the RI and PMI_(—)1 are separately encoded.

In a fourth example, when PMI_(—)1 and the RI are separately encoded,different coding schemes may be used according to the amount ofinformation. For example, if 1 or 2 bits are required to carryinformation included in PMI_(—)1 or the RI, a conventional coding schemeused for ACK/NACK transmission may be adopted. If 3 to 13 bits arerequired, a conventional coding scheme used for CQI transmission may beused.

In a fifth example, PMI_(—)2 and the WB CQI may be transmitted together.In this case, PMI_(—)2 may be a value reflecting a WB. Then feedbackinformation may be transmitted at transmission timings illustrated inTable 20. In Table 20, an RI is transmitted at time T_(—)1, followed byWB PMI_(—)1 at time T_(—)2 and then both WB CQI and WB PMI_(—)2 at timeT_(—)3 in Mode 1-2. In Table 20, Mode 2-2 is defined by adding SB CQItransmission to Mode 2-1.

TABLE 20 T_1 T_2 T_3 T_4~T_N Mode RI Wideband PMI_1 Wideband CQI 1-2Wideband PMI_2 Mode RI Wideband PMI_1 Wideband CQI Best-1 2-2 WidebandPMI_2 CQI in each BPIn a sixth example, CQI may be reported by applying a predetermined PMI(i.e. a PMI preset between a transmitter and a receiver). As aconsequence, the amount of feedback information may be decreased. Forexample, a preset PMI may be used as PMI_(—)2 and the receiver may notfeedback PMI_(—)2 separately. Herein, different PMI_(—)2 values may beused on an arbitrary SB basis.

In a seventh example, PMI_(—)1 may be represented in N bits and PMI_(—)2may be represented in M bits (M<N), when feedback information isconfigured. The amount of the feedback information may vary with a rank.For example, PMI_(—)1 and PMI_(—)2 may be 4 bits and 3 bitsrespectively, for rank-1 transmission. For transmission with a rankhigher than 1, PMI_(—)1 may be represented in fewer than 4 bits andPMI_(—)2 may be represented in fewer than 3 bits.

In an eighth example, when PMI_(—)1 is expressed in fewer than 4 bits, achannel coding scheme used for CQI coding may be applied to PMI_(—)1.

Meanwhile, specific examples of transmitting PMI_(—)1 and WB CQItogether according to the present invention will be described.

In an example, it is assumed that PMI_(—)1 is WB information andPMI_(—)1 and WB CQI are transmitted simultaneously at a transmittingtiming of PMI_(—)1. A PMI should be determined to calculate CQI and thePMI is determined by PMI_(—)1 and PMI_(—)2. Here, PMI_(—)1 may be set toa value transmitted along with the WB CQI and PMI_(—)2 may be a presetvalue. PMI_(—)2 may be information preset on an arbitrary SB basis or ona WB basis. A new PMI may be set using the preset PMI_(—)2 and theselected PMI_(—)1 and the WB CQI may be calculated based on channelinformation changed by applying the new PMI.

In another example, after PMI_(—)1 and the WB CQI are reported, SB CQImay be reported. The SB CQI may be calculated based on the presetPMI_(—)2. In addition, one CQI may be reported for each BP.

In a third example, after PMI_(—)1 and the WB CQI are reported, the SBCQI and PMI_(—)2 may be reported.

Referring to Table 21, a case where WB PMI_(—)1 and SB PMI_(—)2 aretransmitted will be described as a more specific example. In Table 21,Mode 2-2 is a modification example of Mode 2-2 described in Table 12.

TABLE 21 T_1 T_2 T_3 Mode 2-2 RI Wideband PMI_1 Best-1 CQI in each BPWideband CQI Subband PMI_2

As described before, a precoding weight may be a combination of PMI_(—)1and PMI_(—)2. Herein, PMI_(—)1 and PMI_(—)2 are applied to a WB and anSB, respectively. Especially, PMI_(—)2 may be defined as a precodingweight suitable for a BP. A WB may include one or more BPs and a BP mayinclude one or more SBs.

In accordance with an embodiment of the present invention, an RI, WBPMI_(—)1/WB CQI, and SB CQI/SB PMI_(—)2 may be transmitted at differenttime points. As illustrated in Table 21, the RI may be transmitted attime T_(—)1, WB PMI_(—)1 and/or the WB CQI at time T_(—)2, and the SBCQI and/or SB PMI_(—)2 at time T_(—)3. The SB CQI is CQI for an optimumSB (Best-1) selected from a BP. SM PMI_(—)2 is a PMI applied to a BP.The WB CQI may be defined as a value calculated based on a PMI composedof WB PMI_(—)1 and a plurality of BP PMI_(—)2s. The SB CQI is calculatedfor an SB selected from a specific BP. The SB CQI may be calculatedbased on a PMI composed of PMI_(—)1 applied to the WB and PMI_(—)2applied to the BP.

A feedback report on a PUCCH delivers limited information because thePUCCH has a narrow channel space for feedback information, compared to aPUSCH. Accordingly, W1 and W2 may not be fed back simultaneously on thePUCCH. In this case, a WB value may be reported as W2, or a fixed index(i.e. a preset value) may be used as W2.

For example, enhanced PUCCH feedback mode 1-1 may be defined byextending the conventional PUCCH feedback mode 1-1 (a mode of reportingWB CQI and a WB PMI) in order to report WB CQI, WB W1, and fixed W2.

In addition, enhanced PUCCH feedback mode 2-1 may be defined byextending the conventional PUCCH feedback mode 2-1 (a mode of reportingSB CQI and band indication for an SB selected from a BP along with bandcycling, while reporting WB CQI and a WB PMI) in order to report WB CQI,WB W1, fixed W2, SB CQI and band indication for an SB selected from a BPwith band cycling, and SB W2 for the selected band.

To obtain WB CQI in a PUCCH feedback mode, a precoder W should bedetermined. When the precoder W is determined, a precoding matrix indexmay be selected as W1 from a codebook set and W2 may be a fixed index.

PUCCH feedback mode 2-1 may be configured by combining informationreported in PUCCH feedback mode 1-1 with additional CQI/PMI information.The information reported in PUCCH feedback mode 1-1 and the additionalCQI/PMI information may be transmitted at different time points(timings). The additional CQI/PMI information may be dependent on PUCCHfeedback mode 1-1. That is, W1 at the timing of reporting in PUCCHfeedback mode 1-1 is used as precoder information necessary to calculatethe additional CQI information. If WB CQI and WB W1 are missed, nextadditional CQI/PMI information may not be used. W2 that forms theadditional CQI/PMI information may be determined to be a precoder for anSB selected from a BP.

Accordingly, information may be transmitted at transmission timingsillustrated in Table 22 in PUCCH feedback mode 2-1.

TABLE 22 T1 T2 T3 T4 Rank WB CQI SB CQI SB CQI WB W1 SB W2 SB W2 BandIndication Band Indication in bandwidth part N in bandwidth part N + 1

As noted from Table 22, rank information may be transmitted in aduration being integer multiples of reporting durations of WB CQI and SBCQIs, with specific time offsets from the reporting durations of the WBCQI and SB CQIs. If the rank information and CQI/PMI information aretransmitted at the same time, the CQI/PMI information may be dropped.The WB CQI may be calculated based on WB W1 and fixed W2 (preset W2).

A feedback scheme when a multi-granular precoder is defined according toan embodiment of the present invention will now be described.

The multi-granular precoder may be configured of a combination of twodifferent codebooks (W1 and W2). W1 and W2 can be composed of codebooksin various forms. Accordingly, when different types of feedbackindicators (W1 and W2) with respect to precoders are reported to an eNB,the eNB can select the entire precoder. Different pieces of information(W1 and W2) about the precoder may be reported at different timings. Forexample, W1 may be reported in a long term and W2 may be reported in ashort term. When W1 is reported in a long term, RI can be reported withW1. Alternatively, W1 and W2 may be reported simultaneously. That is,when the multi-granular precoder is employed, feedback informationtransmission timings may be set as shown in Table 23.

TABLE 23 T1 T2 Mode (1) Rank + W1(wideband) W2(wideband) + CQI(wideband)Mode (2) Rank W1(wideband) + W2(wideband) + CQI(wideband)

In mode (1) of Table 23, RI and WB W1 may be transmitted at the sametime T1, followed by WB W2 and WB CQI at time T2. In mode (2) of Table23, RI may be transmitted at time T1, followed by WB W1, WB W2 and WBCQI at time T2.

When the indicators W1 and W2 for the precoder are reported at differenttimings or at the same timing, a case in which a PMI/CQI of a limitedrank is fed back may be considered. In this case, W1 and W2 suitable forthe limited rank may be selected and fed back. In addition, CQIcalculated according to the selected W1 and W2 may be fed back. Here,W1, W2 and CQI can be reported at the same time (one subframe).

A scheme of feeding back information including a PMI/CQI of a limitedrank when the multi-granular precoder is applied will now be describedwith reference to FIGS. 22 and 23.

FIG. 22 shows simultaneous transmission of RI and PMI1 (i.e., WB W1)followed by transmission of WB PMI_(—)2 (i.e., WB W2) and WB CQI. Thetransmitted PMI1, PMI2 and CQI are feedback information selected andcalculated according to a rank recommended by a UE. The PMI/CQI of thelimited rank may be transmitted at a timing with a predetermined offset(N_(offset,CQI)) from a CQI/PMI transmission timing according to therank recommended by the UE. FIG. 22 shows transmission of PMI1, PMI_(—)2and CQI according to the limited rank at a timing having a value └Ns/2┘of 2.

FIG. 23 shows transmission of RI followed by simultaneous transmissionof WB PMI1 (i.e., WB W1), WB PMI_(—)2 (i.e., WB W2) and WB CQI. Thetransmitted PMI1, PMI_(—)2 and CQI are feedback information selected andcalculated according to a rank recommended by a UE. The PMI/CQI of thelimited rank may be transmitted at a timing with a predetermined offset(N_(offset,CQI)) from a CQI/PMI transmission timing according to therank recommended by the UE. FIG. 23 shows transmission of PMI1, PMI2 andCQI according to the limited rank at a timing having value └Ns/2┘ of 2.

A feedback scheme when the multi-granular precoder is applied accordingto another embodiment of the present invention will now be described.

When an eNB is reported about multi-granular precoder indicators (i.e.,W1 and W2), different feedback modes can be indicated using a precodertype indication (PTI) bit.

In one feedback mode, RI, W1 and W2/CQI are transmitted in differentsubframes and W1, W2 and CQI are set to WB information. In the otherfeedback mode, W2 and CQI are reported in the same subframe, a frequencygranularity of W2/CQI corresponds to a WB or an SB according to thereported subframe. That is, feedback modes as shown in Table 23 can bedefined.

TABLE 23 T1 T2 T3 Mode (1) PTI(0) + Rank W1(wideband) W2(wideband) +CQI(wideband) Mode (2) PTI(1) + Rank W2(wideband) + W2(subband) +CQI(wideband) CQI(subband)

Referring to Table 23, when the PTI bit is 0, feedback may be performedaccording to a mode in which RI is transmitted at time T1, followed byWB W1 at time T2 and then WB W2 and WB CQI at time T3. When the PTI bitis 1, feedback may be performed according to a mode in which RI istransmitted at time T1, followed by WB W1 and WB CQI at time T2 and thenSB W2 and SB CQI at time T3.

Mode (1) or mode (2) of Table 23 can be determined according to the RIfeedback period. After determining mode (1) or mode (2) by the PTI bit,WB W1 and WB W2/WB CQI may be reported (mode (1)) or WB W2/WB CQI and SBW2/SB CQI may be reported (mode (2)). A reference of the reported periodmay be set to transmission timing. Transmission timing of feedbackinformation other than WB W1/WB CQI can be determined by an offset forthe transmission timing of WB W2/WB CQI.

In the feedback scheme according to the present embodiment, schemes ofsetting a WB W1 feedback period and an offset will now be described.

In accordance with a first scheme, the WB W1 feedback period may be setto be longer than a PTI/RI transmission period (i.e., less frequently).In addition, the WB W1 feedback period may be set to an integer multipleof a WB W2/WB CQI transmission period. In addition, the WB W1transmission timing may be set to an offset value for reference timing(i.e., WB W2/WB CQI transmission subframe).

According to a second scheme, the WB W1 transmission timing may be setto an offset value for the reference timing (i.e., WB W2/WB CQItransmission subframe). When PTI is set to a predetermined value (0or 1) in PTI/RI feedback information, WB W1 can be transmitted one timeright after PTI/RI transmission timing.

In the feedback scheme according to the present embodiment, a scheme offeeding back a PMI/CQI of a limited rank will now be described. WB W1,WB W2, WB CQI, SB W2 and SB CQI are feedback information selected andcalculated according to a rank recommended by a UE, and the PMI/CQI ofthe limited rank may be additionally transmitted.

Provided that PTI reported with RI is set to 0, a WB PMI/WB CQI may bereported as the PMI/CQI of the limited rank. WB W1, WB W2 and WB CQI ofthe limited rank are reported at the same timing. WB W1, WB W2 and WBCQI of the limited rank can be simultaneously reported in some subframesfrom among subframes in which WB W2+WB CQI according to the rankrecommended by the UE are reported.

When PTI reported with RI is set to 1, the PMI/CQI of the limited rankmay be reported. In this case, two schemes may be considered to reportthe PMI/CQI of the limited rank.

One scheme reports only WB W1, WB W2 and WB CQI of the limited rank asthe PMI/CQI of the limited rank.

The other scheme reports WB W1, WB W2 and WB CQI of the limited rank inone subframe and reports SB W2 and SB CQI of the limited rank in adifferent subframe. Transmission timings of WB W1, WB W2 and WB CQI ofthe limited rank and SB W2 and SB CQI of the limited rank may be setaccording to band cyclic reporting period.

Hereinafter, exemplary PUCCH reporting modes are described.

In periodic CQI/PMI/RI transmission, CQI, CQI/PMI, preferred subbandselection and CQI information may be calculated on the basis of the lastreported periodic RI, and subband selection and CQI value may becalculated on the basis of the last reported periodic WB PMI and RI. Twoprecoder indexes (I1 and I2) may be reported at different timings or atthe same timing. Based on this, reporting modes as shown in Table 25 canbe considered in feedback information transmission.

TABLE 25 T1 T2 T3 Mode 1-1-1 (RI + I1)_WB (I2 + CQI)_WB Mode 1-1-2(RI)_WB (I1 + I2 + CQI)_WB Mode Mode 2-1(1) (RI + PTI(0)) (I1)_WB (I2 +2-1 CQI)_WB Mode 2-1(2) (RI + PTI(1)) (I2 + CQI)_WB (I2 + CQI)_SB

In Table 25, I1 and I2 denote indexes of codebooks composed of precoderelements and PTI denotes a precoder type indication bit.

In mode 1-1-1 of Table 23, precoder index I1 indicates the index of aprecoder calculated and selected on the basis of RI transmitted in acurrent subframe, and precoder index I2 indicates the index of aprecoder calculated and selected on the basis of the last reported RIand the last reported I1. CQI represents a value calculated on the basisof the last reported RI, the last reported I1 and currently reported I2.

In mode 1-1-2 of Table 25, precoder indexes I1 and I2 indicate indexesof precoders calculated and selected on the basis of the last reportedRI. CQI represents a value calculated on the basis of the last reportedRI and currently reported I1 and I2.

In mode 2-1(1) of Table 25, precoder index I1 indicates a precoder indexcalculated and selected on the basis of the last reported RI. Precoderindex I2 indicates a precoder index calculated and selected on the basisof the last reported RI and the last reported IL CQI represents a valuecalculated on the basis of the last reported RI, the last reported RIand currently reported I2. When I1 and I2+CQI are reported in an(RI+PTI) transmission period, I1 may be reported one time and I2+CQI maybe reported multiple times. Alternatively, when I1 and I2+CQI arereported in the RI+PTI transmission period, I1 may be reported twice andI2+CQI may be reported multiple times. In addition, I1 may becontinuously reported, or I1 and I2+CQI may be alternately reported.Alternatively, I1 may be reported right after or before RI+PTIreporting.

In mode 2-1(2) of Table 25, precoder index I1 indicates a precoder indexcalculated and selected on the basis of the last reported RI andprecoder index I2 indicates a precoder index calculated and selected onthe basis of the last reported RI and the last reported IL CQIrepresents a value calculated on the basis of the last reported RI, thelast reported I1 and currently reported I2. SB CQI and SB I2 denote avalue and an index calculated and selected on the basis of the lastreported RI and the last reported I1, respectively.

Mode 2-1 of Table 25 will now be described in more detail.

Mode 2-1 (mode 2-1(1) and mode 2-1(2)) of Table 25 may correspond to anextension form of PUCCH reporting mode 2-1 of the above table 5. PUCCHreporting mode of Table 5 is defined in 3GPP LTE release-8/9 system andreports a WB PMI/CQI and SB CQI. Here, SB CQI means CQI of an SBselected in a BP. A BP is a subset of system bandwidths, and a pluralityof SB CQIs may be reported since BPs that can be defined in systembandwidths are selected cyclically according to time and CQIs of the BPsare reported. That is, RI/PMI/CQI can be reported in the time order of(RI)-(WB PMI/CQI)-(SB CQI in a first BP)-(SB CQI in a second BP)- . . .-(SB CQI in an n-th BP). In this case, upon determination of a PMI/CQIreporting period and an offset through RRC signaling, WB PMI/CQI and SBCQI may be reported according to the determined reporting period. RI isset such that it has a period of an integer multiple of the WB PMI/CQIreporting period. The RI may be set such that it is reported beforesubframes corresponding to an offset set using an offset indicator fromWB PMI/CQI transmission timing.

A reporting mode corresponding to an extension form of PUCCH reportingmode 2-1 of Table 5 may be defined as a PUCCH reporting mode in a system(e.g., 3GPP LTE release-10 system) supporting an extended antennaconfiguration.

Similarly to definition of four feedback types (i.e., type 1 correspondsto CQI feedback for a subband selected by a UE, type 2 corresponds to WBCQI feedback and WB PMI feedback, type 3 corresponds to RI feedback,type 4 corresponds to WB CQI feedback) as CQI/PMI/RI feedback types forthe PUCCH reporting mode in 3GPP LTE release-8/9, four CQI/PMI/RIfeedback types can be defined for the PUCCH reporting mode in 3GPP LTErelease-10. For example, reporting type 1 can be defined as RI/PTIfeedback, reporting type 2 can be defined as WB I1 feedback, reportingtype 3 can be defined as WB I2/CQI feedback, and reporting type 4 can bedefined as SB I2/CQI feedback. When PTI of type 1 is set, a reportingtype can be determined. For instance, if PTI of type 1 is 0, type 1-type2-type 3 are used for reporting. When PTI of type 1 is 1, type 1-type3-type 4 are used for reporting. Accordingly, mode 2-1(1) and mode2-1(2) of Table 25 can be defined.

When a precoder element is indicated using one precoder index, PTI isalways set to 1 such that type 1-type 3-type 4 are used for reporting asin the case of transmission using two Tx antennas or transmission usingfour Tx antennas. This scheme is distinguished from the reporting schemeof 3GPP LTE release-8/9 in that SB PMI/CQI is transmitted in type 4. Toallow type-4 transmission in 3GPP LTE release-10 system to be performedas in 3GPP LTE release-8/9 system, one or more BPs in a system bandwidthmay be cyclically reported and a PMI/CQI with respect to a preferred SBin a BP may be reported. In this case, a type 3 or type 4 reportingperiod can be determined through the same method of setting the PMI/CQIreporting period in 3GPP LTE release-8/9 system. For example, type 3 andtype 4 can be reported according to a period set for PMI/CQI. A type 1reporting period can be determined through the same method of setting anRI reporting period in 3GPP LTE release-8/9. For example, the type 1reporting period can be set to an integer multiple of the type 3reporting period. An offset value can be set such that type 1 istransmitted in a subframe a predetermined number of subframes ahead of asubframe in which type 3 is reported.

When precoder elements are indicated using two different precoderindexes as in transmission using eight Tx antennas, (type 1-type 2-type3) or (type 1-type 3-type 4) may be reported according to a PTI value.When two different feedback type sets are selected according to PTI, itis necessary to determine a reporting period for each feedback type.Schemes for signaling the reporting period to be applied to eachfeedback type will now be described.

According to a first scheme, when the type 1 (RI+PTI) reporting periodis set irrespective of a PTI value, the type 1 (RI+PTI) reporting periodcan be set on the basis of type 3 when PTI is 1 (i.e., type 3 in areporting mode corresponding to the order of type 1-type 3-type 4).

According to a second scheme, when the type 1 (RI+PTI) reporting periodis set irrespective of the PTI value, the type 1 (RI+PTI) reportingperiod can be set on the basis of type 3 when PTI is 0 (i.e., type 3 ina reporting mode corresponding to the order of type 1-type 2-type 3).

According to a third scheme, when the type 1 (RI+PTI) reporting periodis set irrespective of a PTI value, the type 1 (RI+PTI) reporting periodcan be set on the basis of type 2 when PTI is 0 (i.e., type 2 in areporting mode corresponding to the order of type 1-type 2-type 3).

According to a fourth scheme, the type 1 (RI+PTI) reporting period canbe set depending on the PTI value. For example, when PTI=1 and one cyclefor transmission of one type 3 (WB I2/CQI) and one or more type 4s (SBI2/CQI) is set, the type 1 (RI+PTI) reporting period can be set to aninteger multiple of the one cycle. When PTI=0 and one cycle fortransmission of one type 2 (WB I1) and one type 3 (WB I2/CQI) is set,the type 1 (RI+PTI(=0)) reporting period can be set to an integermultiple of the one cycle. In this manner, a required minimum cycle canbe set differently when PTI=0 and PTI=1.

According to a fifth scheme, provided that a duration necessary forCQI/PMI transmission when PTI=1 and a duration necessary for CQI/PMItransmission when PTI=0 are different from each other, repeatedtransmission of feedback information can be performed in a shorterduration on the basis of a longer duration. For example, provided thattransmission of one type 2 (WB I1) and one type 3 (WB I2/CQI) isrequired when PTI=0 and transmission of one type 3 (WB I2/CQI) and aplurality of type 4s (SB I2/CQI) is required when PTI=1, the case ofPTI=0 corresponds to a shorter duration and the case of PTI=1corresponds to a longer duration. In this case, the shorter duration canbe repeated to correspond to the longer duration. That is, type 2 and/ortype 3 can be repeatedly transmitted in case of PTI=0. Here, type 3 maybe repeatedly reported after type 2 is reported, or both type 2 and type3 may be repeatedly reported.

According to a sixth scheme, provided that a duration necessary forCQI/PMI transmission when PTI=1 and a duration necessary for CQI/PMItransmission when PTI=0 are different from each other, some of reportedinformation corresponding to a longer duration may be missed andtransmitted in the next type 1 transmission duration on the basis of ashorter duration. For example, provided that transmission of one type 2(WB I1) and one type 3 (WB I2/CQI) is required when PTI=0 andtransmission of one type 3 (WB I2/CQI) and a plurality of type 4s (SBI2/CQI) is required when PTI=1, the case of PTI=0 corresponds to ashorter duration and the case of PTI=1 corresponds to a longer duration.In this case, some information (e.g., type 4) corresponding to thelonger duration can be missed and one type 2 and one type 4 can bereported. If type 4 reports CQI/PMI according to band cycle scheme,CQI/PMI of a different BP may be transmitted according to type 1transmission intervals.

Transmission of Feedback Information on PUSCH

An RI and WB CQI/WB PMI CQI/SB PMI_(—)2 may be fed back on a PUSCH.Various transmission modes may be defined for feedback informationtransmitted on a PUSCH according to the frequency granularity andcombination scheme of transmitted CQI/PMI. Hereinbelow, varioustransmission modes proposed by the present invention, Mode 1-1, Mode1-2, Mode 1-3, Mode 2-2-1, Mode 2-2-2, Mode 2-3, Mode 3-1, and Mode 3-2will be described.

In Mode 1-1, WB CQI for a first CW, WB CQI for a second CW, WB PMI_(—)1,and WB PMI_(—)2 are transmitted. The WB CQI for the first CW may beexpressed as a specific value quantized to N bits. The WB CQI for thesecond CW may also be expressed as a specific value quantized to N bits.For example, N may be 4.

In Mode 1-2, an RI, WB CQI and SB CQIs for a first CW, WB CQI and SBCQIs for a second CW, WB PMI_(—)1, and WM PMI_(—)2 are transmitted. TheWB CQI for the first CW may be expressed as a specific value quantizedto N bits. An SB CQI for the first CW may be expressed in M (M<N) bits,relative to N. The WB CQI for the second CW may also be expressed as aspecific value quantized to N bits. SB CQI for the second CW may beexpressed in M (M<N) bits, relative to N. For example, N may be 4 and Mmay be 2. The SB CQIs are for all SBs included in a total band. Forexample, enhanced PUSCH feedback mode 3-1 for reporting WB CQI, SB CQIs,WB W1, and SB W2s may be defined by applying a W1 and W2 transmissionscheme to a PMI reporting scheme in the conventional PUSCH feedback mode3-1 (a mode of reporting SB CQIs and a WB PMI).

In Mode 1-3, an RI, WB CQI and SB CQI for a first CW, WB CQI and SB CQIfor a second CW, WB PMI_(—)1, SB PMI_(—)2, and the indexes of selectedSBs are transmitted. The WB CQI for the first CW may be expressed as aspecific value quantized to N bits. The SB CQI for the first CW may beexpressed in M (M<N) bits, relative to N. The WB CQI for the second CWmay also be expressed as a specific value quantized to N bits. The SBCQI for the second CW may be expressed in M (M<N) bits, relative to N.For example, N may be 4 and M may be 2. The SB CQI may be an averagevalue of CQIs for SBs selected from all SBs included in a total band. SBPMI_(—)2 may be a selected value suitable for SBs for which SB CQIs arecalculated. In Mode 2-2-1, an RI, WB CQI and SB CQIs for a first CW, WBCQI and SB CQIs for a second CW, WB PMI_(—)1, and SB PMI_(—)2 aretransmitted. The WB CQI for the first CW may be expressed as a specificvalue quantized to N bits. An SB CQI for the first CW may be expressedin M (M<N) bits, relative to N. The WB CQI for the second CW may also beexpressed as a specific value quantized to N bits. An SB CQI for thesecond CW may be expressed in M (M<N) bits, relative to N. For example,N may be 4 and M may be 2. The SB CQIs are for all SBs included in atotal band. SB PMI_(—)2 is also for all SBs included in the total band.

In Mode 2-2-2, an RI, WB CQI and SB CQIs for a first CW, WB CQI and SBCQIs for a second CW, WB PMI_(—)1, and SB PMI_(—)2 are transmitted. TheWB CQI for the first CW may be expressed as a specific value quantizedto N bits. An SB CQI for the first CW may be expressed in M (M<N) bits,relative to N. The WB CQI for the second CW may also be expressed as aspecific value quantized to N bits. An SB CQI for the second CW may beexpressed in M (M<N) bits, relative to N. For example, N may be 4 and Mmay be 2. The SB CQIs are for all SBs included in a total band. SBPMI_(—)2 is also for all BPs included in the total band.

In Mode 2-3, an RI, WB CQI and SB CQIs for a first CW, WB CQI and SBCQIs for a second CW, WB PMI_(—)1, SB PMI_(—)2s, and the indexes ofselected SBs are transmitted. The WB CQI for the first CW may beexpressed as a specific value quantized to N bits. An SB CQI for thefirst CW may be expressed in M (M<N) bits, relative to N. The WB CQI forthe second CW may also be expressed as a specific value quantized to Nbits. An SB CQI for the second CW may be expressed in M (M<N) bits,relative to N. For example, N may be 4 and M may be 2. The SB CQIs arecalculated for SBs selected from all SBs included in a total band,independently for each of the selected SBs. SB PMI_(—)2 s are selectedvalues for SBs for which SB CQIs are calculated, independently for eachof the SBs.

In another example, enhanced PUSCH feedback mode 2-2 for reportingaverage CQI of selected SBs and W2 for the selected SBs may be definedby applying a W1 and W2 transmission scheme to a PMI reporting scheme inthe conventional PUSCH feedback mode 2-2 (a mode of reporting WB CQI, aWB PMI, average CQI of selected SBs, and a PMI for the selected SBs). AWB CQI per codeword may be reported and the WB CQI may be calculated onthe assumption that a single precoding matrix is used for all SBs andtransmission occurs in SBs of a total system bandwidth (set S). Theaverage CQI of the selected SBs may reflect transmission only on Mselected SBs and may be reported as a CQI per codeword calculated usinga selected same precoding matrix for the M SBs. WB W1, WB W2, and W2 forthe selected SBs may be reported in a downlink 8Tx transmission mode inwhich a CSI-RS port is set (transmission mode 9). A UE reports W1 (afirst PMI or i1) for all SBs of the total system bandwidth (set S), W2(a second PMI or i1) for all SBs of the total system bandwidth (set S),and W2 (a second PMI) for M selected SBs.

In Mode 3-1, WB CQI for a first CW, WB CQI for a second CW, WB PMI_(—)1,and SB PMI_(—)2 s are transmitted. Each of the WB CQI for the first CWand the WB CQI for the second CW may be expressed as a specific valuequantized to N bits. For example, N may be 4. SB PMI_(—)2 s are for allSBs included in a total band. For instance, CQI is reported for a WB anda PMI is reported for an SB in PUSCH feedback mode 1-2 defined in the3GPP LTE Release-8 system and the PMI reporting scheme may be extendedto feedback of W1 and W2. For example, enhanced PUSCH feedback mode 1-2may be defined to report WB CQI, WB W1, and SB W2s. One WB CQI percodeword is reported and the WB CQI is calculated on the assumption thata selected precoding matrix is used for each SB and transmission occursin the SBs of a total system bandwidth (set S). WB W1 (a first PMI ori1) and SB W2s (second PMIs or i2s) may be reported in the downlink 8Txtransmission mode in which a CSI-RS port is set (transmission mode 9).Herein, WB W1 (the first PMI or i1) may be reported for the total systembandwidth (set S) and WB W2 (the second PMI or i2) may be reported foreach SB in the total system bandwidth (set S). In Mode 3-2, WB CQI for afirst CW, WB CQI for a second CW, WB PMI_(—)1, and an SB PMI_(—)2 aretransmitted. Each of the WB CQI for the first CW and the WB CQI for thesecond CW may be expressed as a specific value quantized to N bits. Forexample, N may be 4. SB PMI_(—)2 is for all BPs included in a totalband.

As described before, an RI may be separately encoded and CQI and a PMImay be jointly encoded in the various modes for transmitting feedbackinformation on a PUSCH. The RI and the CQI and/or the PMI may betransmitted simultaneously on the PUSCH.

The multi-precoder reporting methods have been described above toimprove feedback in the system supporting an extended antennaconfiguration (e.g. 3GPP LTE-A). That is, an overall precoder W may becreated by combining two precoders W1 and W2 (W=W1·W2). Herein, W1 islong-term reported WB information and W2 is short-term reported SBinformation. However, W2 may be reported in a different manner dependingon feedback overhead. For example, the reporting period and/or reportedtarget (WB/SB) of W2 may be different in PUSCH feedback and PUCCHfeedback.

In PUSCH feedback, W1 and W2 may be reported simultaneously because aPUSCH has a wide channel capacity for carrying feedback information,relative to a PUCCH. Both W1 and W2 may be WB information, or W1 may beWB information and W2 may be SB information.

For example, enhanced PUSCH feedback mode 1-2 may be defined to reportWB CQI, WB W1, and SB W2s. One WB CQI per codeword is reported and theWB CQI is calculated on the assumption that a selected precoding matrixis used for each SB and transmission occurs in the SBs of a total systembandwidth (set S). WB W1 (a first PMI or i1) and SB W2s (second PMIs ori2s) may be reported in the downlink 8Tx transmission mode in which aCSI-RS port is set (transmission mode 9). Herein, WB W1 (the first PMIor i1) may be reported for the total system bandwidth (set S) and WB W2(the second PMI or i2) may be reported for each SB in the total systembandwidth (set S).

In a similar manner, enhanced PUSCH feedback mode 2-2 for reportingaverage CQI of selected SBs and W2 for the selected SBs may be definedby applying a W1 and W2 transmission scheme to a PMI reporting scheme inthe conventional PUSCH feedback mode 2-2 (a mode of reporting WB CQI, aWB PMI, average CQI of selected SBs, and a PMI for the selected SBs). AWB CQI per codeword may be reported and the WB CQI may be calculated onthe assumption that a single precoding matrix is used for all SBs andtransmission occurs in SBs of a total system bandwidth (set S). Theaverage CQI of the selected SBs may reflect transmission only on Mselected SBs and may be reported as a CQI per codeword calculated usinga selected same precoding matrix for the M SBs. WB W1, WB W2, and W2 forthe selected SBs may be reported in a downlink 8Tx transmission mode inwhich a CSI-RS port is set (transmission mode 9). A UE reports W1 (afirst PMI or i1) for all SBs of the total system bandwidth (set S), W2(a second PMI or i1) for all SBs of the total system bandwidth (set S),and W2 (a second PMI) for M selected SBs.

In a similar manner, enhanced PUSCH feedback mode 3-1 for reporting SBCQIs, WB W1 and SB W2s may be defined by applying a W1 and W2transmission scheme to a PMI reporting scheme in the conventional PUSCHfeedback mode 3-1 (a mode of reporting SB CQIs and a WB PMI).

As described before, enhanced PUSCH feedback modes 1-2, 2-2, and 3-1 maybe summarized in Table 26.

TABLE 26 PMI Feedback Type With PMI (CL) PUSCH Wideband Mode 1-2:Multiple PMI CQI CQI Wideband CQI for 1^(st) CW feedback Wideband CQIfor 2^(nd) CW if RI >1 Type Wideband W1 Subband W2 on each subband UEMode 2-2: Multiple PMI Selected Wideband CQI for 1^(st) CW CQI for1^(st) CW on M subband Wideband CQI for 2^(nd) CW if RI >1 CQI for2^(nd) CW on M subband if RI >1 Wideband W1 Wideband W2 W2 on M subbandSelected subband Indicator Higher Mode 3-1: Single PMI layer SubbandCQIs for 1^(st) CW on each subband configured Wideband CQI for 2^(nd) CWif RI >1 Subband CQIs for 2^(nd) CW on each subband if RI >1 Wideband W1Wideband W2

A CSI reporting method according to an embodiment of the presentinvention is described with reference to FIG. 24.

A UE may measure a downlink channel state regarding a downlinktransmission from an eNB and feedback the downlink channel statemeasurement to the eNB on uplink. For example, when the eNB uses 8 Txantennas for the downlink transmission, the eNB may transmit CSI-RSsthrough 8 antenna ports (antenna port 15 to antenna port 22). The UE maytransmit the results of measuring a downlink channel state in theCSI-RSs (an RI, a PMI, CQI, etc.). Various examples of the presentinvention may be applied to select and calculate an RI/PMI/CQI. The eNBmay determine the number of layers, a precoder, and an MCS level fordownlink transmission based on the CSI (RI/PMI/CQI) and transmit adownlink signal based on the determined information.

Referring to FIG. 24, the UE may feed back an RI through a first uplinksubframe (S2410). The UE may feed back a first PMI through a seconduplink subframe (S2420). The UE may feed back a second PMI and CQIthrough a third uplink subframe (S2430).

Here, an RI transmission timing, a first PMI transmission timing and asecond PMI and CQI transmission timing (that is, the first, second andthird subframes) can be determined according to above-describedexemplary embodiments of the present invention.

A preferred precoding matrix of a UE can be indicated by a combinationof the first PMI and the second PMI. For example, the first PMI canindicate precoding matrix candidates applied to the downlinktransmission and the second PMI can indicate one of the precoding matrixcandidates.

The CSI (the RI, the first PMI, the second PMI and CQI) may betransmitted in the respective uplink subframes over a PUCCH. That is,the CSI (the RI, the first PMI, the second PMI and CQI) can beperiodically transmitted according to reporting periods thereof. The CSIreporting periods may be determined according to the above-mentionedvarious embodiments of the present invention.

The first PMI, the second PMI and CQI may be feedback informationregarding a WB.

The descriptions of the above various embodiments of the presentinvention may be applied alone or in a combination of two or more inrelation to the CSI transmission method of the present inventiondescribed with reference to FIG. 24. A redundant description will not beprovided herein, for clarity.

In addition, CSI feedback for MIMO transmission between an eNB and an RN(a backhaul uplink and a backhaul downlink) and CSI feedback for MIMOtransmission between an RN and a UE (an access uplink and an accessdownlink) may be implemented based on the same principle of the presentinvention.

FIG. 25 is a block diagram of an eNB and a UE according to the presentinvention.

Referring to FIG. 25, an eNB 2510 according to the present invention mayinclude an Rx module 2511, a Tx module 2512, a processor 2513, a memory2514, and a plurality of antennas 2515. The existence of the pluralityof antennas 2515 means that the eNB 2510 supports MIMO transmission andreception. The Rx module 2511 may receive uplink signals, data, andinformation from UEs. The Tx module 2512 may transmit downlink signals,data, and information to UEs. The processor 2513 may provide overallcontrol to the eNB 2510. In accordance with an embodiment of the presentinvention, the eNB 2510 may be configured so as to transmit downlinksignals through up to 8 Tx antennas and receive CSI regarding a downlinktransmission from a UE 2520. The processor 2513 may be configured toreceive an RI in a first subframe, receive a first PMI in a secondsubframe and receive a second PMI and CQI in a third subframe throughthe Rx module 2511. A preferred precoding matrix of the UE may beindicated by a combination of the first PMI and the second PMI.

The processor 5313 processes information received at the eNB 2510,information to be transmitted to the outside, etc. The memory 2514 maystore the processed information for a predetermined time and may bereplaced by a component like a buffer (not shown).

The UE 2520 according to the present invention may include an Rx module2521, a Tx module 2522, a processor 2523, a memory 2524, and a pluralityof antennas 2525. The existence of the plurality of antennas 2525 meansthat the UE 2520 supports MIMO transmission and reception. The Rx module2521 may receive downlink signals, data, and information from an eNB.The Tx module 2522 may transmit uplink signals, data, and information toan eNB. The processor 2523 may provide overall control to the UE 2520.

In accordance with an embodiment of the present invention, the UE 2520may be configured so as to receive downlink signals through up to 8 Txantennas from the eNB 2510 and feed back CSI regarding the downlinktransmission to the eNB 2510. The processor 2523 may be configured totransmit an RI in a first subframe, transmit a first PMI in a secondsubframe and transmit a second PMI and CQI in a third subframe throughthe Tx module 2522. A preferred precoding matrix of the UE may beindicated by a combination of the first PMI and the second PMI.

The processor 2523 of the UE 2520 processes information received at theUE 2520, information to be transmitted to the outside, etc. The memory2524 may store the processed information for a predetermined time andmay be replaced by a component like a buffer (not shown).

The descriptions of the foregoing various embodiments of the presentinvention may be applied alone or in a combination of two or more to thespecific configurations of the eNB and the UE. A redundant descriptionis not provided herein for clarity.

The description of the eNB 2510 in FIG. 25 may be applied to an RN as adownlink transmission entity or an uplink reception entity, and thedescription of the UE 2520 in FIG. 25 may be applied to an RN as adownlink reception entity or an uplink transmission entity.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof.

In a hardware configuration, the methods according to the embodiments ofthe present invention may be achieved by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSDPs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit is located at the interior or exteriorof the processor and may transmit and receive data to and from theprocessor via various known means.

The detailed description of the preferred embodiments of the presentinvention is given to enable those skilled in the art to realize andimplement the present invention. While the present invention has beendescribed referring to the preferred embodiments of the presentinvention, those skilled in the art will appreciate that manymodifications and changes can be made to the present invention withoutdeparting from the spirit and essential characteristics of the presentinvention. For example, the structures of the above-describedembodiments of the present invention can be used in combination. Theabove embodiments are therefore to be construed in all aspects asillustrative and not restrictive. Therefore, the present inventionintends not to limit the embodiments disclosed herein but to give abroadest range matching the principles and new features disclosedherein.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. Therefore, the present invention intends not tolimit the embodiments disclosed herein but to give a broadest rangematching the principles and new features disclosed herein. It is obviousto those skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

The methods for effectively reporting feedback information in amulti-antenna system according to the above-described embodiments of thepresent invention are applicable to various multi-antenna mobilecommunication systems (all mobile communication systems based onmultiple access schemes such as OFDMA, SC-FDMA, CDMA, TDMA etc.).

1. A method for periodically transmitting channel state informationthrough an uplink channel in a wireless communication system, the methodcomprising: transmitting a rank indicator (RI) in a first subframe;transmitting a first precoding matrix indicator (PMI) in a secondsubframe; and transmitting a second PMI and a channel quality indicator(CQI) in a third subframe, wherein the first PMI indicates precodingmatrix candidates and the second PMI indicates one of the precodingmatrix candidates, wherein the RI is transmitted according to a firstreporting period, wherein the first precoding matrix is transmittedaccording to a second reporting period, the second PMI and the CQI aretransmitted according to a third reporting period, and wherein thesecond reporting period is equal to or shorter than the first reportingperiod, and the second reporting period is longer than the thirdreporting period.
 2. The method according to claim 1, wherein a specificoffset is applied between the first subframe and the second subframe. 3.The method according to claim 1, wherein a preferred precoding matrix ofa user equipment (UE) is indicated by a combination of the first PMI andthe second PMI.
 4. The method according to claim 1, wherein the uplinkchannel is a physical uplink control channel (PUCCH).
 5. The methodaccording to claim 1, wherein the RI, the first PMI, the second PMI andthe CQI correspond to channel state information for downlink 8-transmitantenna transmission.
 6. The method according to claim 1, wherein thefirst PMI is a wideband first PMI.
 7. The method according to claim 1,wherein the second PMI is a wideband second PMI.
 8. The method accordingto claim 1, wherein the CQI is a wideband CQI.
 9. A method forperiodically receiving channel state information through an uplink in awireless communication system, the method comprising: receiving a rankindicator (RI) in a first subframe; receiving a first precoding matrixindicator (PMI) in a second subframe; and receiving a second PMI and achannel quality indicator (CQI) in a third subframe, wherein the firstPMI indicates precoding matrix candidates and the second PMI indicatesone of the precoding matrix candidates, wherein the RI is transmittedaccording to a first reporting period, wherein the first precodingmatrix is transmitted according to a second reporting period, the secondPMI and the CQI are transmitted according to a third reporting period,and wherein the second reporting period is equal to or shorter than thefirst reporting period, and the second reporting period is longer thanthe third reporting period.
 10. A user equipment (UE) for periodicallytransmitting channel state information through an uplink channel in awireless communication system, the UE comprising: a reception module; atransmission module; and a processor, wherein the processor isconfigured to; transmit, using the transmission module, a rank indicator(RI) in a first subframe; transmit, using the transmission module, afirst precoding matrix indicator (PMI) in a second subframe; andtransmit, using the transmission module, a second PMI and a channelquality indicator (CQI) in a third subframe, wherein the first PMIindicates precoding matrix candidates and the second PMI indicates oneof the precoding matrix candidates, wherein the RI is transmittedaccording to a first reporting period, wherein the first precodingmatrix is transmitted according to a second reporting period, the secondPMI and the CQI are transmitted according to a third reporting period,and wherein the second reporting period is equal to or shorter than thefirst reporting period, and the second reporting period is longer thanthe third reporting period.
 11. An evolved Node B (eNB) for receivingchannel state information through an uplink channel in a wirelesscommunication system, the eNB comprising: a reception module; atransmission module; and a processor, wherein the processor isconfigured to: receive, using the reception module, a rank indicator(RI) in a first subframe; receive, using the reception module, a firstprecoding matrix indicator (PMI) in a second subframe; and receive,using the reception module, a second PMI and a channel quality indicator(CQI) in a third subframe, wherein the first PMI indicates precodingmatrix candidates and the second PMI indicates one of the precodingmatrix candidates, wherein the RI is transmitted according to a firstreporting period, wherein the first precoding matrix is transmittedaccording to a second reporting period, the second PMI and the CQI aretransmitted according to a third reporting period, and wherein thesecond reporting period is equal to or shorter than the first reportingperiod, and the second reporting period is longer than the thirdreporting period.